Added support for structs and strings in unions.

(C++ only for now).
Also fixed vector of union support in the object API.

Bug: 36902939
Change-Id: I935f4cc2c303a4728e26c7916a8ec0adcd6f84cb
Tested: on Linux.

docs/source/CppUsage.md

@@ -411,4 +411,22 @@ manually wrap it in synchronisation primites. There's no automatic way to
 accomplish this, by design, as we feel multithreaded construction
 of a single buffer will be rare, and synchronisation overhead would be costly.
 
+## Advanced union features
+
+The C++ implementation currently supports vectors of unions (i.e. you can
+declare a field as `[T]` where `T` is a union type instead of a table type). It
+also supports structs and strings in unions, besides tables.
+
+For an example of these features, see `tests/union_vector`, and
+`UnionVectorTest` in `test.cpp`.
+
+Since these features haven't been ported to other languages yet, if you
+choose to use them, you won't be able to use these buffers in other languages
+(`flatc` will refuse to compile a schema that uses these features).
+
+These features reduce the amount of "table wrapping" that was previously
+needed to use unions.
+
+To use scalars, simply wrap them in a struct.
+
 <br>

include/flatbuffers/flatbuffers.h

@@ -360,6 +360,8 @@ private:
   const uint8_t *data_;
 };
 
+struct String;
+
 // This is used as a helper type for accessing vectors.
 // Vector::data() assumes the vector elements start after the length field.
 template<typename T> class Vector {
@@ -391,6 +393,18 @@ public:
     return static_cast<E>(Get(i));
   }
 
+  // If this a vector of unions, this does the cast for you. There's no check
+  // to make sure this is the right type!
+  template<typename U> const U *GetAs(uoffset_t i) const {
+    return reinterpret_cast<const U *>(Get(i));
+  }
+
+  // If this a vector of unions, this does the cast for you. There's no check
+  // to make sure this is actually a string!
+  const String *GetAsString(uoffset_t i) const {
+    return reinterpret_cast<const String *>(Get(i));
+  }
+
   const void *GetStructFromOffset(size_t o) const {
     return reinterpret_cast<const void *>(Data() + o);
   }
@@ -1327,6 +1341,13 @@ FLATBUFFERS_FINAL_CLASS
                                      reinterpret_cast<uint8_t **>(buf));
   }
 
+  /// @brief Write a struct by itself, typically to be part of a union.
+  template<typename T> Offset<const T *> CreateStruct(const T &structobj) {
+    Align(AlignOf<T>());
+    buf_.push_small(structobj);
+    return Offset<const T *>(GetSize());
+  }
+
   /// @brief The length of a FlatBuffer file header.
   static const size_t kFileIdentifierLength = 4;
 

include/flatbuffers/idl.h

@@ -283,18 +283,18 @@ inline size_t InlineAlignment(const Type &type) {
 
 struct EnumVal {
   EnumVal(const std::string &_name, int64_t _val)
-    : name(_name), value(_val), struct_def(nullptr) {}
+    : name(_name), value(_val) {}
 
   Offset<reflection::EnumVal> Serialize(FlatBufferBuilder *builder) const;
 
   std::string name;
   std::vector<std::string> doc_comment;
   int64_t value;
-  StructDef *struct_def;  // only set if this is a union
+  Type union_type;
 };
 
 struct EnumDef : public Definition {
-  EnumDef() : is_union(false) {}
+  EnumDef() : is_union(false), uses_type_aliases(false) {}
 
   EnumVal *ReverseLookup(int enum_idx, bool skip_union_default = true) {
     for (auto it = vals.vec.begin() + static_cast<int>(is_union &&
@@ -312,6 +312,7 @@ struct EnumDef : public Definition {
 
   SymbolTable<EnumVal> vals;
   bool is_union;
+  bool uses_type_aliases;
   Type underlying_type;
 };
 
@@ -548,6 +549,7 @@ private:
                                      const std::string &name, const Type &type,
                                      FieldDef **dest);
   FLATBUFFERS_CHECKED_ERROR ParseField(StructDef &struct_def);
+  FLATBUFFERS_CHECKED_ERROR ParseString(Value &val);
   FLATBUFFERS_CHECKED_ERROR ParseAnyValue(Value &val, FieldDef *field,
                                           size_t parent_fieldn,
                                           const StructDef *parent_struct_def);

include/flatbuffers/reflection_generated.h

@@ -204,7 +204,8 @@ struct EnumVal FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   enum {
     VT_NAME = 4,
     VT_VALUE = 6,
-    VT_OBJECT = 8
+    VT_OBJECT = 8,
+    VT_UNION_TYPE = 10
   };
   const flatbuffers::String *name() const {
     return GetPointer<const flatbuffers::String *>(VT_NAME);
@@ -228,6 +229,9 @@ struct EnumVal FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   const Object *object() const {
     return GetPointer<const Object *>(VT_OBJECT);
   }
+  const Type *union_type() const {
+    return GetPointer<const Type *>(VT_UNION_TYPE);
+  }
   bool Verify(flatbuffers::Verifier &verifier) const {
     return VerifyTableStart(verifier) &&
            VerifyFieldRequired<flatbuffers::uoffset_t>(verifier, VT_NAME) &&
@@ -235,6 +239,8 @@ struct EnumVal FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
            VerifyField<int64_t>(verifier, VT_VALUE) &&
            VerifyField<flatbuffers::uoffset_t>(verifier, VT_OBJECT) &&
            verifier.VerifyTable(object()) &&
+           VerifyField<flatbuffers::uoffset_t>(verifier, VT_UNION_TYPE) &&
+           verifier.VerifyTable(union_type()) &&
            verifier.EndTable();
   }
 };
@@ -251,13 +257,16 @@ struct EnumValBuilder {
   void add_object(flatbuffers::Offset<Object> object) {
     fbb_.AddOffset(EnumVal::VT_OBJECT, object);
   }
+  void add_union_type(flatbuffers::Offset<Type> union_type) {
+    fbb_.AddOffset(EnumVal::VT_UNION_TYPE, union_type);
+  }
   EnumValBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }
   EnumValBuilder &operator=(const EnumValBuilder &);
   flatbuffers::Offset<EnumVal> Finish() {
-    const auto end = fbb_.EndTable(start_, 3);
+    const auto end = fbb_.EndTable(start_, 4);
     auto o = flatbuffers::Offset<EnumVal>(end);
     fbb_.Required(o, EnumVal::VT_NAME);
     return o;
@@ -268,9 +277,11 @@ inline flatbuffers::Offset<EnumVal> CreateEnumVal(
     flatbuffers::FlatBufferBuilder &_fbb,
     flatbuffers::Offset<flatbuffers::String> name = 0,
     int64_t value = 0,
-    flatbuffers::Offset<Object> object = 0) {
+    flatbuffers::Offset<Object> object = 0,
+    flatbuffers::Offset<Type> union_type = 0) {
   EnumValBuilder builder_(_fbb);
   builder_.add_value(value);
+  builder_.add_union_type(union_type);
   builder_.add_object(object);
   builder_.add_name(name);
   return builder_.Finish();
@@ -280,12 +291,14 @@ inline flatbuffers::Offset<EnumVal> CreateEnumValDirect(
     flatbuffers::FlatBufferBuilder &_fbb,
     const char *name = nullptr,
     int64_t value = 0,
-    flatbuffers::Offset<Object> object = 0) {
+    flatbuffers::Offset<Object> object = 0,
+    flatbuffers::Offset<Type> union_type = 0) {
   return reflection::CreateEnumVal(
       _fbb,
       name ? _fbb.CreateString(name) : 0,
       value,
-      object);
+      object,
+      union_type);
 }
 
 struct Enum FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {

reflection/reflection.fbs

@@ -42,7 +42,8 @@ table KeyValue {
 table EnumVal {
     name:string (required);
     value:long (key);
-    object:Object;  // Only if part of a union.
+    object:Object;  // Will be deprecated in favor of union_type in the future.
+    union_type:Type;
 }
 
 table Enum {

samples/monster_generated.h

@@ -71,35 +71,35 @@ template<> struct EquipmentTraits<Weapon> {
 
 struct EquipmentUnion {
   Equipment type;
-  flatbuffers::NativeTable *table;
+  void *value;
 
-  EquipmentUnion() : type(Equipment_NONE), table(nullptr) {}
+  EquipmentUnion() : type(Equipment_NONE), value(nullptr) {}
   EquipmentUnion(EquipmentUnion&& u) FLATBUFFERS_NOEXCEPT :
-    type(Equipment_NONE), table(nullptr)
-    { std::swap(type, u.type); std::swap(table, u.table); }
+    type(Equipment_NONE), value(nullptr)
+    { std::swap(type, u.type); std::swap(value, u.value); }
   EquipmentUnion(const EquipmentUnion &);
   EquipmentUnion &operator=(const EquipmentUnion &);
   EquipmentUnion &operator=(EquipmentUnion &&u) FLATBUFFERS_NOEXCEPT
-    { std::swap(type, u.type); std::swap(table, u.table); return *this; }
+    { std::swap(type, u.type); std::swap(value, u.value); return *this; }
   ~EquipmentUnion() { Reset(); }
 
   void Reset();
 
   template <typename T>
-  void Set(T&& value) {
+  void Set(T&& val) {
     Reset();
     type = EquipmentTraits<typename T::TableType>::enum_value;
     if (type != Equipment_NONE) {
-      table = new T(std::forward<T>(value));
+      value = new T(std::forward<T>(val));
     }
   }
 
-  static flatbuffers::NativeTable *UnPack(const void *obj, Equipment type, const flatbuffers::resolver_function_t *resolver);
+  static void *UnPack(const void *obj, Equipment type, const flatbuffers::resolver_function_t *resolver);
   flatbuffers::Offset<void> Pack(flatbuffers::FlatBufferBuilder &_fbb, const flatbuffers::rehasher_function_t *_rehasher = nullptr) const;
 
   WeaponT *AsWeapon() {
     return type == Equipment_Weapon ?
-      reinterpret_cast<WeaponT *>(table) : nullptr;
+      reinterpret_cast<WeaponT *>(value) : nullptr;
   }
 };
 
@@ -228,7 +228,7 @@ struct Monster FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   }
   template<typename T> const T *equipped_as() const;
   const Weapon *equipped_as_Weapon() const {
-    return (equipped_type() == Equipment_Weapon)? static_cast<const Weapon *>(equipped()) : nullptr;
+    return equipped_type() == Equipment_Weapon ? static_cast<const Weapon *>(equipped()) : nullptr;
   }
   void *mutable_equipped() {
     return GetPointer<void *>(VT_EQUIPPED);
@@ -451,7 +451,7 @@ inline void Monster::UnPackTo(MonsterT *_o, const flatbuffers::resolver_function
   { auto _e = color(); _o->color = _e; };
   { auto _e = weapons(); if (_e) { _o->weapons.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->weapons[_i] = std::unique_ptr<WeaponT>(_e->Get(_i)->UnPack(_resolver)); } } };
   { auto _e = equipped_type(); _o->equipped.type = _e; };
-  { auto _e = equipped(); if (_e) _o->equipped.table = EquipmentUnion::UnPack(_e, equipped_type(),_resolver); };
+  { auto _e = equipped(); if (_e) _o->equipped.value = EquipmentUnion::UnPack(_e, equipped_type(), _resolver); };
 }
 
 inline flatbuffers::Offset<Monster> Monster::Pack(flatbuffers::FlatBufferBuilder &_fbb, const MonsterT* _o, const flatbuffers::rehasher_function_t *_rehasher) {
@@ -535,7 +535,7 @@ inline bool VerifyEquipmentVector(flatbuffers::Verifier &verifier, const flatbuf
   return true;
 }
 
-inline flatbuffers::NativeTable *EquipmentUnion::UnPack(const void *obj, Equipment type, const flatbuffers::resolver_function_t *resolver) {
+inline void *EquipmentUnion::UnPack(const void *obj, Equipment type, const flatbuffers::resolver_function_t *resolver) {
   switch (type) {
     case Equipment_Weapon: {
       auto ptr = reinterpret_cast<const Weapon *>(obj);
@@ -548,7 +548,7 @@ inline flatbuffers::NativeTable *EquipmentUnion::UnPack(const void *obj, Equipme
 inline flatbuffers::Offset<void> EquipmentUnion::Pack(flatbuffers::FlatBufferBuilder &_fbb, const flatbuffers::rehasher_function_t *_rehasher) const {
   switch (type) {
     case Equipment_Weapon: {
-      auto ptr = reinterpret_cast<const WeaponT *>(table);
+      auto ptr = reinterpret_cast<const WeaponT *>(value);
       return CreateWeapon(_fbb, ptr, _rehasher).Union();
     }
     default: return 0;
@@ -558,13 +558,13 @@ inline flatbuffers::Offset<void> EquipmentUnion::Pack(flatbuffers::FlatBufferBui
 inline void EquipmentUnion::Reset() {
   switch (type) {
     case Equipment_Weapon: {
-      auto ptr = reinterpret_cast<WeaponT *>(table);
+      auto ptr = reinterpret_cast<WeaponT *>(value);
       delete ptr;
       break;
     }
     default: break;
   }
-  table = nullptr;
+  value = nullptr;
   type = Equipment_NONE;
 }
 

src/idl_gen_cpp.cpp

@@ -109,7 +109,7 @@ class CppGenerator : public BaseGenerator {
         SetNameSpace(struct_def.defined_namespace);
         code_ += "struct " + struct_def.name + ";";
         if (parser_.opts.generate_object_based_api && !struct_def.fixed) {
-          code_ += "struct " + NativeName(struct_def.name) + ";";
+          code_ += "struct " + NativeName(struct_def.name, &struct_def) + ";";
         }
         code_ += "";
       }
@@ -239,7 +239,7 @@ class CppGenerator : public BaseGenerator {
       if (parser_.opts.generate_object_based_api) {
         // A convenient root unpack function.
         auto native_name =
-            NativeName(WrapInNameSpace(struct_def));
+            NativeName(WrapInNameSpace(struct_def), &struct_def);
         code_.SetValue("UNPACK_RETURN",
                        GenTypeNativePtr(native_name, nullptr, false));
         code_.SetValue("UNPACK_TYPE",
@@ -355,7 +355,9 @@ class CppGenerator : public BaseGenerator {
   }
 
   // TODO(wvo): make this configurable.
-  static std::string NativeName(const std::string &name) { return name + "T"; }
+  static std::string NativeName(const std::string &name, const StructDef *sd) {
+    return sd && !sd->fixed ? name + "T" : name;
+  }
 
   const std::string &PtrType(const FieldDef *field) {
     auto attr = field ? field->attributes.Lookup("cpp_ptr_type") : nullptr;
@@ -411,7 +413,8 @@ class CppGenerator : public BaseGenerator {
             return GenTypeNativePtr(type_name, &field, false);
           }
         } else {
-          return GenTypeNativePtr(NativeName(type_name), &field, false);
+          return GenTypeNativePtr(NativeName(type_name, type.struct_def),
+                                  &field, false);
         }
       }
       case BASE_TYPE_UNION: {
@@ -458,6 +461,26 @@ class CppGenerator : public BaseGenerator {
     }
   }
 
+  std::string StripUnionType(const std::string &name) {
+    return name.substr(0, name.size() - strlen(UnionTypeFieldSuffix()));
+  }
+
+  std::string GetUnionElement(const EnumVal &ev, bool wrap, bool actual_type,
+                              bool native_type = false) {
+    if (ev.union_type.base_type == BASE_TYPE_STRUCT) {
+      auto name = actual_type ? ev.union_type.struct_def->name : ev.name;
+      return wrap
+          ? WrapInNameSpace(ev.union_type.struct_def->defined_namespace, name)
+          : name;
+    } else if (ev.union_type.base_type == BASE_TYPE_STRING) {
+      return actual_type
+          ? (native_type ? "std::string" : "flatbuffers::String")
+          : ev.name;
+    } else {
+      assert(false);
+    }
+  }
+
   static std::string UnionVerifySignature(const EnumDef &enum_def) {
     return "bool Verify" + enum_def.name +
            "(flatbuffers::Verifier &verifier, const void *obj, " +
@@ -474,7 +497,7 @@ class CppGenerator : public BaseGenerator {
   static std::string UnionUnPackSignature(const EnumDef &enum_def,
                                           bool inclass) {
     return (inclass ? "static " : "") +
-           std::string("flatbuffers::NativeTable *") +
+           std::string("void *") +
            (inclass ? "" : enum_def.name + "Union::") +
            "UnPack(const void *obj, " + enum_def.name +
            " type, const flatbuffers::resolver_function_t *resolver)";
@@ -493,7 +516,7 @@ class CppGenerator : public BaseGenerator {
     return "flatbuffers::Offset<" + struct_def.name + "> Create" +
            struct_def.name  +
            "(flatbuffers::FlatBufferBuilder &_fbb, const " +
-           NativeName(struct_def.name) +
+           NativeName(struct_def.name, &struct_def) +
            " *_o, const flatbuffers::rehasher_function_t *_rehasher" +
            (predecl ? " = nullptr" : "") + ")";
   }
@@ -504,14 +527,14 @@ class CppGenerator : public BaseGenerator {
            "flatbuffers::Offset<" + struct_def.name + "> " +
            (inclass ? "" : struct_def.name + "::") +
            "Pack(flatbuffers::FlatBufferBuilder &_fbb, " +
-           "const " + NativeName(struct_def.name) + "* _o, " +
+           "const " + NativeName(struct_def.name, &struct_def) + "* _o, " +
            "const flatbuffers::rehasher_function_t *_rehasher" +
            (inclass ? " = nullptr" : "") + ")";
   }
 
   static std::string TableUnPackSignature(const StructDef &struct_def,
                                           bool inclass) {
-    return NativeName(struct_def.name) + " *" +
+    return NativeName(struct_def.name, &struct_def) + " *" +
            (inclass ? "" : struct_def.name + "::") +
            "UnPack(const flatbuffers::resolver_function_t *_resolver" +
            (inclass ? " = nullptr" : "") + ") const";
@@ -520,8 +543,8 @@ class CppGenerator : public BaseGenerator {
   static std::string TableUnPackToSignature(const StructDef &struct_def,
                                             bool inclass) {
     return "void " + (inclass ? "" : struct_def.name + "::") +
-           "UnPackTo(" + NativeName(struct_def.name) + " *" + "_o, " +
-           "const flatbuffers::resolver_function_t *_resolver" +
+           "UnPackTo(" + NativeName(struct_def.name, &struct_def) + " *" +
+           "_o, const flatbuffers::resolver_function_t *_resolver" +
            (inclass ? " = nullptr" : "") + ") const";
   }
 
@@ -629,7 +652,7 @@ class CppGenerator : public BaseGenerator {
     }
 
     // Generate type traits for unions to map from a type to union enum value.
-    if (enum_def.is_union) {
+    if (enum_def.is_union && !enum_def.uses_type_aliases) {
       for (auto it = enum_def.vals.vec.begin(); it != enum_def.vals.vec.end();
         ++it) {
         const auto &ev = **it;
@@ -638,7 +661,7 @@ class CppGenerator : public BaseGenerator {
           code_ += "template<typename T> struct {{ENUM_NAME}}Traits {";
         }
         else {
-          auto name = WrapInNameSpace(*ev.struct_def);
+          auto name = GetUnionElement(ev, true, true);
           code_ += "template<> struct {{ENUM_NAME}}Traits<" + name + "> {";
         }
 
@@ -657,29 +680,31 @@ class CppGenerator : public BaseGenerator {
 
       code_ += "struct {{NAME}}Union {";
       code_ += "  {{NAME}} type;";
-      code_ += "  flatbuffers::NativeTable *table;";
+      code_ += "  void *value;";
       code_ += "";
-      code_ += "  {{NAME}}Union() : type({{NONE}}), table(nullptr) {}";
+      code_ += "  {{NAME}}Union() : type({{NONE}}), value(nullptr) {}";
       code_ += "  {{NAME}}Union({{NAME}}Union&& u) FLATBUFFERS_NOEXCEPT :";
-      code_ += "    type({{NONE}}), table(nullptr)";
-      code_ += "    { std::swap(type, u.type); std::swap(table, u.table); }";
+      code_ += "    type({{NONE}}), value(nullptr)";
+      code_ += "    { std::swap(type, u.type); std::swap(value, u.value); }";
       code_ += "  {{NAME}}Union(const {{NAME}}Union &);";
       code_ += "  {{NAME}}Union &operator=(const {{NAME}}Union &);";
       code_ += "  {{NAME}}Union &operator=({{NAME}}Union &&u) FLATBUFFERS_NOEXCEPT";
-      code_ += "    { std::swap(type, u.type); std::swap(table, u.table); return *this; }";
+      code_ += "    { std::swap(type, u.type); std::swap(value, u.value); return *this; }";
       code_ += "  ~{{NAME}}Union() { Reset(); }";
       code_ += "";
       code_ += "  void Reset();";
       code_ += "";
+      if (!enum_def.uses_type_aliases) {
         code_ += "  template <typename T>";
-      code_ += "  void Set(T&& value) {";
+        code_ += "  void Set(T&& val) {";
         code_ += "    Reset();";
         code_ += "    type = {{NAME}}Traits<typename T::TableType>::enum_value;";
         code_ += "    if (type != {{NONE}}) {";
-      code_ += "      table = new T(std::forward<T>(value));";
+        code_ += "      value = new T(std::forward<T>(val));";
         code_ += "    }";
         code_ += "  }";
         code_ += "";
+      }
       code_ += "  " + UnionUnPackSignature(enum_def, true) + ";";
       code_ += "  " + UnionPackSignature(enum_def, true) + ";";
       code_ += "";
@@ -691,14 +716,16 @@ class CppGenerator : public BaseGenerator {
           continue;
         }
 
-        const auto native_type = NativeName(WrapInNameSpace(*ev.struct_def));
+        const auto native_type =
+            NativeName(GetUnionElement(ev, true, true, true),
+                       ev.union_type.struct_def);
         code_.SetValue("NATIVE_TYPE", native_type);
         code_.SetValue("NATIVE_NAME", ev.name);
         code_.SetValue("NATIVE_ID", GetEnumValUse(enum_def, ev));
 
         code_ += "  {{NATIVE_TYPE}} *As{{NATIVE_NAME}}() {";
         code_ += "    return type == {{NATIVE_ID}} ?";
-        code_ += "      reinterpret_cast<{{NATIVE_TYPE}} *>(table) : nullptr;";
+        code_ += "      reinterpret_cast<{{NATIVE_TYPE}} *>(value) : nullptr;";
         code_ += "  }";
       }
       code_ += "};";
@@ -728,10 +755,23 @@ class CppGenerator : public BaseGenerator {
       code_.SetValue("LABEL", GetEnumValUse(enum_def, ev));
 
       if (ev.value) {
-        code_.SetValue("TYPE", WrapInNameSpace(*ev.struct_def));
+        code_.SetValue("TYPE", GetUnionElement(ev, true, true));
         code_ += "    case {{LABEL}}: {";
-        code_ += "      auto ptr = reinterpret_cast<const {{TYPE}} *>(obj);";
+        auto getptr =
+            "      auto ptr = reinterpret_cast<const {{TYPE}} *>(obj);";
+        if (ev.union_type.base_type == BASE_TYPE_STRUCT) {
+          if (ev.union_type.struct_def->fixed) {
+            code_ += "      return true;";
+          } else {
+            code_ += getptr;
             code_ += "      return verifier.VerifyTable(ptr);";
+          }
+        } else if (ev.union_type.base_type == BASE_TYPE_STRING) {
+          code_ += getptr;
+          code_ += "      return verifier.Verify(ptr);";
+        } else {
+          assert(false);
+        }
         code_ += "    }";
       } else {
         code_ += "    case {{LABEL}}: {";
@@ -768,10 +808,21 @@ class CppGenerator : public BaseGenerator {
         }
 
         code_.SetValue("LABEL", GetEnumValUse(enum_def, ev));
-        code_.SetValue("TYPE", WrapInNameSpace(*ev.struct_def));
+        code_.SetValue("TYPE", GetUnionElement(ev, true, true));
         code_ += "    case {{LABEL}}: {";
         code_ += "      auto ptr = reinterpret_cast<const {{TYPE}} *>(obj);";
+        if (ev.union_type.base_type == BASE_TYPE_STRUCT) {
+          if (ev.union_type.struct_def->fixed) {
+            code_ += "      return new " +
+                     WrapInNameSpace(*ev.union_type.struct_def) + "(*ptr);";
+          } else {
             code_ += "      return ptr->UnPack(resolver);";
+          }
+        } else if (ev.union_type.base_type == BASE_TYPE_STRING) {
+          code_ += "      return new std::string(ptr->c_str(), ptr->size());";
+        } else {
+          assert(false);
+        }
         code_ += "    }";
       }
       code_ += "    default: return nullptr;";
@@ -789,11 +840,23 @@ class CppGenerator : public BaseGenerator {
         }
 
         code_.SetValue("LABEL", GetEnumValUse(enum_def, ev));
-        code_.SetValue("TYPE", NativeName(WrapInNameSpace(*ev.struct_def)));
-        code_.SetValue("NAME", ev.struct_def->name);
+        code_.SetValue("TYPE", NativeName(GetUnionElement(ev, true, true, true),
+                                          ev.union_type.struct_def));
+        code_.SetValue("NAME", GetUnionElement(ev, false, true));
         code_ += "    case {{LABEL}}: {";
-        code_ += "      auto ptr = reinterpret_cast<const {{TYPE}} *>(table);";
-        code_ += "      return Create{{NAME}}(_fbb, ptr, _rehasher).Union();";
+        code_ += "      auto ptr = reinterpret_cast<const {{TYPE}} *>(value);";
+        if (ev.union_type.base_type == BASE_TYPE_STRUCT) {
+          if (ev.union_type.struct_def->fixed) {
+            code_ += "      return _fbb.CreateStruct(*ptr).Union();";
+          } else {
+            code_ +=
+                "      return Create{{NAME}}(_fbb, ptr, _rehasher).Union();";
+          }
+        } else if (ev.union_type.base_type == BASE_TYPE_STRING) {
+          code_ += "      return _fbb.CreateString(*ptr).Union();";
+        } else {
+          assert(false);
+        }
         code_ += "    }";
       }
       code_ += "    default: return 0;";
@@ -815,17 +878,18 @@ class CppGenerator : public BaseGenerator {
         }
 
         code_.SetValue("LABEL", GetEnumValUse(enum_def, ev));
-        code_.SetValue("TYPE", NativeName(WrapInNameSpace(*ev.struct_def)));
+        code_.SetValue("TYPE", NativeName(GetUnionElement(ev, true, true, true),
+                                          ev.union_type.struct_def));
 
         code_ += "    case {{LABEL}}: {";
-        code_ += "      auto ptr = reinterpret_cast<{{TYPE}} *>(table);";
+        code_ += "      auto ptr = reinterpret_cast<{{TYPE}} *>(value);";
         code_ += "      delete ptr;";
         code_ += "      break;";
         code_ += "    }";
       }
       code_ += "    default: break;";
       code_ += "  }";
-      code_ += "  table = nullptr;";
+      code_ += "  value = nullptr;";
       code_ += "  type = {{NONE}};";
       code_ += "}";
       code_ += "";
@@ -914,7 +978,9 @@ class CppGenerator : public BaseGenerator {
   // Generate a member, including a default value for scalars and raw pointers.
   void GenMember(const FieldDef &field) {
     if (!field.deprecated &&  // Deprecated fields won't be accessible.
-        field.value.type.base_type != BASE_TYPE_UTYPE) {
+        field.value.type.base_type != BASE_TYPE_UTYPE &&
+        (field.value.type.base_type != BASE_TYPE_VECTOR ||
+         field.value.type.element != BASE_TYPE_UTYPE)) {
       auto type = GenTypeNative(field.value.type, false, field);
       auto cpp_type = field.attributes.Lookup("cpp_type");
       auto full_type = (cpp_type ? cpp_type->constant + " *" : type + " ");
@@ -964,7 +1030,7 @@ class CppGenerator : public BaseGenerator {
       initializer_list = "\n      : " + initializer_list;
     }
 
-    code_.SetValue("NATIVE_NAME", NativeName(struct_def.name));
+    code_.SetValue("NATIVE_NAME", NativeName(struct_def.name, &struct_def));
     code_.SetValue("INIT_LIST", initializer_list);
 
     code_ += "  {{NATIVE_NAME}}(){{INIT_LIST}} {";
@@ -972,7 +1038,7 @@ class CppGenerator : public BaseGenerator {
   }
 
   void GenNativeTable(const StructDef &struct_def) {
-    const auto native_name = NativeName(struct_def.name);
+    const auto native_name = NativeName(struct_def.name, &struct_def);
     code_.SetValue("STRUCT_NAME", struct_def.name);
     code_.SetValue("NATIVE_NAME", native_name);
 
@@ -1138,24 +1204,23 @@ class CppGenerator : public BaseGenerator {
 
         for (auto u_it = u->vals.vec.begin();
              u_it != u->vals.vec.end(); ++u_it) {
-          if (!(*u_it)->struct_def) {
+          auto &ev = **u_it;
+          if (ev.union_type.base_type == BASE_TYPE_NONE) {
             continue;
           }
-          auto arg_struct_def = (*u_it)->struct_def;
-          auto full_struct_name = WrapInNameSpace(*arg_struct_def);
+          auto full_struct_name = GetUnionElement(ev, true, true);
 
           // @TODO: Mby make this decisions more universal? How?
           code_.SetValue("U_GET_TYPE", field.name + UnionTypeFieldSuffix());
           code_.SetValue("U_ELEMENT_TYPE", WrapInNameSpace(
-                         u->defined_namespace, GetEnumValUse(*u, **u_it)));
+                         u->defined_namespace, GetEnumValUse(*u, ev)));
           code_.SetValue("U_FIELD_TYPE", "const " + full_struct_name + " *");
-          code_.SetValue("U_ELEMENT_NAME", full_struct_name);
           code_.SetValue("U_FIELD_NAME",
-                         field.name + "_as_" + (*u_it)->name);
+                         field.name + "_as_" + ev.name);
 
           // `const Type *union_name_asType() const` accessor.
           code_ += "  {{U_FIELD_TYPE}}{{U_FIELD_NAME}}() const {";
-          code_ += "    return ({{U_GET_TYPE}}() == {{U_ELEMENT_TYPE}})? "
+          code_ += "    return {{U_GET_TYPE}}() == {{U_ELEMENT_TYPE}} ? "
                   "static_cast<{{U_FIELD_TYPE}}>({{FIELD_NAME}}()) "
                   ": nullptr;";
           code_ += "  }";
@@ -1279,23 +1344,25 @@ class CppGenerator : public BaseGenerator {
       }
 
       auto u = field.value.type.enum_def;
+      if (u->uses_type_aliases) continue;
+
       code_.SetValue("FIELD_NAME", field.name);
 
       for (auto u_it = u->vals.vec.begin();
            u_it != u->vals.vec.end(); ++u_it) {
-        if (!(*u_it)->struct_def) {
+        auto &ev = **u_it;
+        if (ev.union_type.base_type == BASE_TYPE_NONE) {
           continue;
         }
 
-        auto arg_struct_def = (*u_it)->struct_def;
-        auto full_struct_name = WrapInNameSpace(*arg_struct_def);
+        auto full_struct_name = GetUnionElement(ev, true, true);
 
         code_.SetValue("U_ELEMENT_TYPE", WrapInNameSpace(
-                       u->defined_namespace, GetEnumValUse(*u, **u_it)));
+                       u->defined_namespace, GetEnumValUse(*u, ev)));
         code_.SetValue("U_FIELD_TYPE", "const " + full_struct_name + " *");
         code_.SetValue("U_ELEMENT_NAME", full_struct_name);
         code_.SetValue("U_FIELD_NAME",
-                       field.name + "_as_" + (*u_it)->name);
+                       field.name + "_as_" + ev.name);
 
         // `template<> const T *union_name_as<T>() const` accessor.
         code_ += "template<> "
@@ -1475,6 +1542,14 @@ class CppGenerator : public BaseGenerator {
     }
   }
 
+  std::string GenUnionUnpackVal(const FieldDef &afield,
+                                const char *vec_elem_access,
+                                const char *vec_type_access) {
+    return afield.value.type.enum_def->name + "Union::UnPack(" + "_e" +
+           vec_elem_access + ", " + afield.name + UnionTypeFieldSuffix() +
+           "()" + vec_type_access + ", _resolver)";
+  }
+
   std::string GenUnpackVal(const Type &type, const std::string &val,
                            bool invector, const FieldDef &afield) {
     switch (type.base_type) {
@@ -1494,10 +1569,18 @@ class CppGenerator : public BaseGenerator {
             return ptype + "(new " + name + "(*" + val + "))";
           }
         } else {
-          const auto ptype = GenTypeNativePtr(NativeName(name), &afield, true);
+          const auto ptype = GenTypeNativePtr(NativeName(name, type.struct_def),
+                                              &afield, true);
           return ptype + "(" + val + "->UnPack(_resolver))";
         }
       }
+      case BASE_TYPE_UNION: {
+        return GenUnionUnpackVal(afield,
+                                 invector ? "->Get(_i)" : "",
+                                 invector ? ("->GetEnum<" +
+                                             type.enum_def->name +
+                                             ">(_i)").c_str() : "");
+      }
       default: {
         return val;
         break;
@@ -1523,10 +1606,19 @@ class CppGenerator : public BaseGenerator {
         //   for (uoffset_t i = 0; i < _e->size(); ++i) {
         //     _o->field.push_back(_e->Get(_i));
         //   }
-        code += "{ _o->" + field.name + ".resize(_e->size()); ";
+        auto name = field.name;
+        if (field.value.type.element == BASE_TYPE_UTYPE) {
+          name = StripUnionType(field.name);
+        }
+        auto access = field.value.type.element == BASE_TYPE_UTYPE
+                        ? ".type"
+                        : (field.value.type.element == BASE_TYPE_UNION
+                          ? ".value"
+                          : "");
+        code += "{ _o->" + name + ".resize(_e->size()); ";
         code += "for (flatbuffers::uoffset_t _i = 0;";
         code += " _i < _e->size(); _i++) { ";
-        code += "_o->" + field.name + "[_i] = ";
+        code += "_o->" + name + "[_i]" + access + " = ";
         code += GenUnpackVal(field.value.type.VectorType(),
                                   indexing, true, field);
         code += "; } }";
@@ -1540,12 +1632,11 @@ class CppGenerator : public BaseGenerator {
         break;
       }
       case BASE_TYPE_UNION: {
-        // Generate code that sets the union table, of the form:
-        //   _o->field.table = Union::Unpack(_e, field_type(), resolver);
-        code += "_o->" + field.name + ".table = ";
-        code += field.value.type.enum_def->name + "Union::UnPack(";
-        code += "_e, " + field.name + UnionTypeFieldSuffix() + "(),";
-        code += "_resolver);";
+        // Generate code that sets the union value, of the form:
+        //   _o->field.value = Union::Unpack(_e, field_type(), resolver);
+        code += "_o->" + field.name + ".value = ";
+        code += GenUnionUnpackVal(field, "", "");
+        code += ";";
         break;
       }
       default: {
@@ -1577,8 +1668,7 @@ class CppGenerator : public BaseGenerator {
   std::string GenCreateParam(const FieldDef &field) {
     std::string value = "_o->";
     if (field.value.type.base_type == BASE_TYPE_UTYPE) {
-      value += field.name.substr(0, field.name.size() -
-                                 strlen(UnionTypeFieldSuffix()));
+      value += StripUnionType(field.name);
       value += ".type";
     } else {
       value += field.name;
@@ -1635,6 +1725,19 @@ class CppGenerator : public BaseGenerator {
             code += "_fbb.CreateVector(" + value + ")";
             break;
           }
+          case BASE_TYPE_UNION: {
+            code += "_fbb.CreateVector<flatbuffers::Offset<void>>(" + value +
+                    ".size(), [&](size_t i) { return " + value +
+                    "[i].Pack(_fbb, _rehasher); })";
+            break;
+          }
+          case BASE_TYPE_UTYPE: {
+            value = StripUnionType(value);
+            code += "_fbb.CreateVector<uint8_t>(" + value +
+                    ".size(), [&](size_t i) { return static_cast<uint8_t>(" + value +
+                    "[i].type); })";
+            break;
+          }
           default: {
             if (field.value.type.enum_def) {
               // For enumerations, we need to get access to the array data for
@@ -1693,7 +1796,7 @@ class CppGenerator : public BaseGenerator {
   // Generate code for tables that needs to come after the regular definition.
   void GenTablePost(const StructDef &struct_def) {
     code_.SetValue("STRUCT_NAME", struct_def.name);
-    code_.SetValue("NATIVE_NAME", NativeName(struct_def.name));
+    code_.SetValue("NATIVE_NAME", NativeName(struct_def.name, &struct_def));
 
     if (parser_.opts.generate_object_based_api) {
       // Generate the X::UnPack() method.

src/idl_gen_js.cpp

@@ -71,7 +71,8 @@ namespace js {
 class JsGenerator : public BaseGenerator {
  public:
   typedef std::unordered_set<std::string> imported_fileset;
-  typedef std::unordered_multimap<std::string, ReexportDescription> reexport_map;
+  typedef std::unordered_multimap<std::string, ReexportDescription>
+          reexport_map;
 
   JsGenerator(const Parser &parser, const std::string &path,
               const std::string &file_name)
@@ -104,19 +105,22 @@ class JsGenerator : public BaseGenerator {
     code += enum_code;
     code += struct_code;
 
-    if (lang_.language == IDLOptions::kJs && !exports_code.empty() && !parser_.opts.skip_js_exports) {
+    if (lang_.language == IDLOptions::kJs && !exports_code.empty() &&
+        !parser_.opts.skip_js_exports) {
       code += "// Exports for Node.js and RequireJS\n";
       code += exports_code;
     }
 
-    return SaveFile(GeneratedFileName(path_, file_name_, lang_).c_str(), code, false);
+    return SaveFile(GeneratedFileName(path_, file_name_, lang_).c_str(), code,
+                    false);
   }
 
  private:
   JsLanguageParameters lang_;
 
   // Generate code for imports
-  void generateImportDependencies(std::string *code_ptr, const imported_fileset &imported_files) {
+  void generateImportDependencies(std::string *code_ptr,
+                                  const imported_fileset &imported_files) {
     std::string &code = *code_ptr;
     for (auto it = imported_files.begin(); it != imported_files.end(); ++it) {
       const auto &file = *it;
@@ -129,11 +133,13 @@ class JsGenerator : public BaseGenerator {
     }
   }
 
-  // Generate reexports, which might not have been explicitly imported using the "export import" trick
+  // Generate reexports, which might not have been explicitly imported using the
+  // "export import" trick
   void generateReexports(std::string *code_ptr,
                          const reexport_map &reexports,
                          imported_fileset imported_files) {
-      if (!parser_.opts.reexport_ts_modules || lang_.language != IDLOptions::kTs) {
+      if (!parser_.opts.reexport_ts_modules ||
+          lang_.language != IDLOptions::kTs) {
           return;
       }
 
@@ -152,7 +158,9 @@ class JsGenerator : public BaseGenerator {
 
           code += "export namespace " + file.second.target_namespace + " { \n";
           code += "export import " + file.second.symbol + " = ";
-          code += GenFileNamespacePrefix(file.first) + "." + file.second.source_namespace + "." + file.second.symbol + "; }\n";
+          code += GenFileNamespacePrefix(file.first) + "." +
+                  file.second.source_namespace + "." + file.second.symbol +
+                  "; }\n";
         }
       }
   }
@@ -175,11 +183,13 @@ class JsGenerator : public BaseGenerator {
     for (auto it = parser_.structs_.vec.begin();
          it != parser_.structs_.vec.end(); ++it) {
       auto &struct_def = **it;
-      GenStruct(parser_, struct_def, decl_code_ptr, exports_code_ptr, imported_files);
+      GenStruct(parser_, struct_def, decl_code_ptr, exports_code_ptr,
+                imported_files);
     }
   }
   void GenNamespaces(std::string *code_ptr, std::string *exports_ptr) {
-  if (lang_.language == IDLOptions::kTs && parser_.opts.skip_flatbuffers_import) {
+  if (lang_.language == IDLOptions::kTs &&
+      parser_.opts.skip_flatbuffers_import) {
     return;
   }
 
@@ -282,13 +292,14 @@ void GenEnum(EnumDef &enum_def, std::string *code_ptr,
   std::string &exports = *exports_ptr;
   GenDocComment(enum_def.doc_comment, code_ptr, "@enum");
   if (lang_.language == IDLOptions::kTs) {
-    code += "export namespace " + GetNameSpace(enum_def) + "{\n" + "export enum " + enum_def.name + "{\n";
+    code += "export namespace " + GetNameSpace(enum_def) + "{\n" +
+            "export enum " + enum_def.name + "{\n";
   } else {
     if (enum_def.defined_namespace->components.empty()) {
       code += "var ";
       if(parser_.opts.use_goog_js_export_format) {
-        exports += "goog.exportSymbol('" + enum_def.name + "', " + enum_def.name +
-          ");\n";
+        exports += "goog.exportSymbol('" + enum_def.name + "', " +
+                   enum_def.name + ");\n";
       } else {
         exports += "this." + enum_def.name + " = " + enum_def.name + ";\n";
       }
@@ -304,12 +315,19 @@ void GenEnum(EnumDef &enum_def, std::string *code_ptr,
       }
       GenDocComment(ev.doc_comment, code_ptr, "", "  ");
     }
-    code += "  " + ev.name + ((lang_.language == IDLOptions::kTs) ? ("= ") : (": ")) + NumToString(ev.value);
+    code += "  " + ev.name;
+    code += lang_.language == IDLOptions::kTs ? "= " : ": ";
+    code += NumToString(ev.value);
     code += (it + 1) != enum_def.vals.vec.end() ? ",\n" : "\n";
 
-    if (ev.struct_def) {
-        ReexportDescription desc = { ev.name, GetNameSpace(*ev.struct_def), GetNameSpace(enum_def) };
-        reexports.insert(std::make_pair(ev.struct_def->file, std::move(desc)));
+    if (ev.union_type.struct_def) {
+        ReexportDescription desc = {
+          ev.name,
+          GetNameSpace(*ev.union_type.struct_def),
+          GetNameSpace(enum_def)
+        };
+        reexports.insert(std::make_pair(ev.union_type.struct_def->file,
+                                        std::move(desc)));
     }
   }
 
@@ -366,7 +384,8 @@ std::string GenDefaultValue(const Value &value, const std::string &context) {
     if (auto val = value.type.enum_def->ReverseLookup(
         atoi(value.constant.c_str()), false)) {
       if (lang_.language == IDLOptions::kTs) {
-        return GenPrefixedTypeName(WrapInNameSpace(*value.type.enum_def), value.type.enum_def->file) + "." + val->name;
+        return GenPrefixedTypeName(WrapInNameSpace(*value.type.enum_def),
+                                   value.type.enum_def->file) + "." + val->name;
       } else {
         return WrapInNameSpace(*value.type.enum_def) + "." + val->name;
       }
@@ -448,17 +467,21 @@ static std::string MaybeScale(T value) {
 }
 
 static std::string GenFileNamespacePrefix(const std::string &file) {
-  return "NS" + std::to_string(static_cast<unsigned long long>(std::hash<std::string>()(file)));
+  return "NS" + std::to_string(
+        static_cast<unsigned long long>(std::hash<std::string>()(file)));
 }
 
 static std::string GenPrefixedImport(const std::string &full_file_name,
                                      const std::string &base_file_name) {
-  return "import * as "+ GenFileNamespacePrefix(full_file_name) + " from \"./" + base_file_name + "\";\n";
+  return "import * as "+ GenFileNamespacePrefix(full_file_name) +
+         " from \"./" + base_file_name + "\";\n";
 }
 
 // Adds a source-dependent prefix, for of import * statements.
-std::string GenPrefixedTypeName(const std::string &typeName, const std::string &file) {
-  const auto basename = flatbuffers::StripPath(flatbuffers::StripExtension(file));
+std::string GenPrefixedTypeName(const std::string &typeName,
+                                const std::string &file) {
+  const auto basename =
+      flatbuffers::StripPath(flatbuffers::StripExtension(file));
   if (basename == file_name_) {
     return typeName;
   }
@@ -483,7 +506,8 @@ void GenStructArgs(const StructDef &struct_def,
       *annotations += "} " + nameprefix + field.name + "\n";
 
       if (lang_.language == IDLOptions::kTs) {
-          *arguments += ", " + nameprefix + field.name + ": " + GenTypeName(field.value.type, true);
+          *arguments += ", " + nameprefix + field.name + ": " +
+                        GenTypeName(field.value.type, true);
       } else {
           *arguments += ", " + nameprefix + field.name;
       }
@@ -521,7 +545,8 @@ static void GenStructBody(const StructDef &struct_def,
 }
 
 // Generate an accessor struct with constructor for a flatbuffers struct.
-void GenStruct(const Parser &parser, StructDef &struct_def, std::string *code_ptr, std::string *exports_ptr,
+void GenStruct(const Parser &parser, StructDef &struct_def,
+               std::string *code_ptr, std::string *exports_ptr,
                imported_fileset &imported_files) {
   if (struct_def.generated) return;
   std::string &code = *code_ptr;
@@ -583,7 +608,8 @@ void GenStruct(const Parser &parser, StructDef &struct_def, std::string *code_pt
   code += " */\n";
 
   if (lang_.language == IDLOptions::kTs) {
-    code += "__init(i:number, bb:flatbuffers.ByteBuffer):" + object_name + " {\n";
+    code += "__init(i:number, bb:flatbuffers.ByteBuffer):" + object_name +
+            " {\n";
   } else {
     code += object_name + ".prototype.__init = function(i, bb) {\n";
   }
@@ -602,7 +628,8 @@ void GenStruct(const Parser &parser, StructDef &struct_def, std::string *code_pt
       "@returns {" + object_name + "}");
     if (lang_.language == IDLOptions::kTs) {
       code += "static getRootAs" + struct_def.name;
-      code += "(bb:flatbuffers.ByteBuffer, obj?:" + object_name + "):" + object_name + " {\n";
+      code += "(bb:flatbuffers.ByteBuffer, obj?:" + object_name + "):" +
+              object_name + " {\n";
     } else {
       code += object_name + ".getRootAs" + struct_def.name;
       code += " = function(bb, obj) {\n";
@@ -618,7 +645,8 @@ void GenStruct(const Parser &parser, StructDef &struct_def, std::string *code_pt
         "@param {flatbuffers.ByteBuffer} bb\n"
         "@returns {boolean}");
       if (lang_.language == IDLOptions::kTs) {
-        code += "static bufferHasIdentifier(bb:flatbuffers.ByteBuffer):boolean {\n";
+        code +=
+            "static bufferHasIdentifier(bb:flatbuffers.ByteBuffer):boolean {\n";
       } else {
         code += object_name + ".bufferHasIdentifier = function(bb) {\n";
       }
@@ -647,13 +675,16 @@ void GenStruct(const Parser &parser, StructDef &struct_def, std::string *code_pt
         std::string prefix = MakeCamel(field.name, false) + "(";
         if (field.value.type.base_type == BASE_TYPE_STRING) {
           code += prefix + "):string\n";
-          code += prefix + "optionalEncoding:flatbuffers.Encoding"+"):" + GenTypeName(field.value.type, false)+"\n";
+          code += prefix + "optionalEncoding:flatbuffers.Encoding"+"):" +
+                  GenTypeName(field.value.type, false)+"\n";
           code += prefix + "optionalEncoding?:any";
         } else {
           code += prefix;
         }
         if (field.value.type.enum_def) {
-          code += "):" + GenPrefixedTypeName(GenTypeName(field.value.type, false), field.value.type.enum_def->file) + " {\n";
+          code += "):" +
+                  GenPrefixedTypeName(GenTypeName(field.value.type, false),
+                                      field.value.type.enum_def->file) + " {\n";
         } else {
           code += "):" + GenTypeName(field.value.type, false) + " {\n";
         }
@@ -733,12 +764,14 @@ void GenStruct(const Parser &parser, StructDef &struct_def, std::string *code_pt
             std::string prefix = MakeCamel(field.name, false);
             prefix += "(index: number";
             if (vectortype.base_type == BASE_TYPE_STRUCT) {
-              vectortypename = GenPrefixedTypeName(vectortypename, vectortype.struct_def->file);
+              vectortypename = GenPrefixedTypeName(vectortypename,
+                                                   vectortype.struct_def->file);
               code += prefix + ", obj?:" + vectortypename;
               imported_files.insert(vectortype.struct_def->file);
             } else if (vectortype.base_type == BASE_TYPE_STRING) {
               code += prefix + "):string\n";
-              code += prefix + ",optionalEncoding:flatbuffers.Encoding" + "):" + vectortypename + "\n";
+              code += prefix + ",optionalEncoding:flatbuffers.Encoding" + "):" +
+                      vectortypename + "\n";
               code += prefix + ",optionalEncoding?:any";
             } else {
               code += prefix;
@@ -819,31 +852,37 @@ void GenStruct(const Parser &parser, StructDef &struct_def, std::string *code_pt
 
     // Adds the mutable scalar value to the output
     if (IsScalar(field.value.type.base_type) && parser.opts.mutable_buffer) {
-      std::string annotations = "@param {" + GenTypeName(field.value.type, true) + "} value\n";
+      std::string annotations =
+          "@param {" + GenTypeName(field.value.type, true) + "} value\n";
       GenDocComment(code_ptr, annotations +
         "@returns {boolean}");
 
       if (lang_.language == IDLOptions::kTs) {
         std::string type;
         if (field.value.type.enum_def) {
-          type = GenPrefixedTypeName(GenTypeName(field.value.type, true), field.value.type.enum_def->file);
+          type = GenPrefixedTypeName(GenTypeName(field.value.type, true),
+                                     field.value.type.enum_def->file);
         } else {
           type = GenTypeName(field.value.type, true);
         }
 
         code += "mutate_" + field.name + "(value:" + type + "):boolean {\n";
       } else {
-        code += object_name + ".prototype.mutate_" + field.name + " = function(value) {\n";
+        code += object_name + ".prototype.mutate_" + field.name +
+                " = function(value) {\n";
       }
 
-      code += "  var offset = this.bb.__offset(this.bb_pos, " + NumToString(field.value.offset) + ");\n\n";
+      code += "  var offset = this.bb.__offset(this.bb_pos, " +
+              NumToString(field.value.offset) + ");\n\n";
       code += "  if (offset === 0) {\n";
       code += "    return false;\n";
       code += "  }\n\n";
 
       // special case for bools, which are treated as uint8
-      code += "  this.bb.write" + MakeCamel(GenType(field.value.type)) + "(this.bb_pos + offset, ";
-      if (field.value.type.base_type == BASE_TYPE_BOOL && lang_.language == IDLOptions::kTs) {
+      code += "  this.bb.write" + MakeCamel(GenType(field.value.type)) +
+              "(this.bb_pos + offset, ";
+      if (field.value.type.base_type == BASE_TYPE_BOOL &&
+          lang_.language == IDLOptions::kTs) {
           code += "+";
       }
 
@@ -885,7 +924,8 @@ void GenStruct(const Parser &parser, StructDef &struct_def, std::string *code_pt
 
         if (lang_.language == IDLOptions::kTs) {
           code += MakeCamel(field.name, false);
-          code += "Array():" + GenType(vectorType) + "Array {\n" + offset_prefix;
+          code += "Array():" + GenType(vectorType) + "Array {\n" +
+                  offset_prefix;
         } else {
           code += object_name + ".prototype." + MakeCamel(field.name, false);
           code += "Array = function() {\n" + offset_prefix;
@@ -958,13 +998,15 @@ void GenStruct(const Parser &parser, StructDef &struct_def, std::string *code_pt
       if (lang_.language == IDLOptions::kTs) {
         std::string argType;
         if (field.value.type.enum_def) {
-          argType = GenPrefixedTypeName(GenTypeName(field.value.type, true), field.value.type.enum_def->file);
+          argType = GenPrefixedTypeName(GenTypeName(field.value.type, true),
+                                        field.value.type.enum_def->file);
         } else {
           argType = GenTypeName(field.value.type, true);
         }
 
         code += "static add" + MakeCamel(field.name);
-        code += "(builder:flatbuffers.Builder, " + argname + ":" + argType + ") {\n";
+        code += "(builder:flatbuffers.Builder, " + argname + ":" + argType +
+                ") {\n";
       } else {
         code += object_name + ".add" + MakeCamel(field.name);
         code += " = function(builder, " + argname + ") {\n";
@@ -1005,7 +1047,8 @@ void GenStruct(const Parser &parser, StructDef &struct_def, std::string *code_pt
             if (type == "number[]") {
               type += " | Uint8Array";
             }
-            code += "Vector(builder:flatbuffers.Builder, data:" + type+"):flatbuffers.Offset {\n";
+            code += "Vector(builder:flatbuffers.Builder, data:" + type +
+                    "):flatbuffers.Offset {\n";
             code += "if(!data){\n  return null\n}\n";
           } else {
             code += object_name + ".create" + MakeCamel(field.name);

src/idl_gen_text.cpp

@@ -49,7 +49,7 @@ void OutputIdentifier(const std::string &name, const IDLOptions &opts,
 // for a single FlatBuffer value into JSON format.
 // The general case for scalars:
 template<typename T> bool Print(T val, Type type, int /*indent*/,
-                                StructDef * /*union_sd*/,
+                                Type */*union_type*/,
                                 const IDLOptions &opts,
                                 std::string *_text) {
   std::string &text = *_text;
@@ -169,22 +169,16 @@ static bool EscapeString(const String &s, std::string *_text, const IDLOptions&
 // Specialization of Print above for pointer types.
 template<> bool Print<const void *>(const void *val,
                                     Type type, int indent,
-                                    StructDef *union_sd,
+                                    Type *union_type,
                                     const IDLOptions &opts,
                                     std::string *_text) {
   switch (type.base_type) {
     case BASE_TYPE_UNION:
       // If this assert hits, you have an corrupt buffer, a union type field
       // was not present or was out of range.
-      assert(union_sd);
-      if (!GenStruct(*union_sd,
-                     reinterpret_cast<const Table *>(val),
-                     indent,
-                     opts,
-                     _text)) {
-        return false;
-      }
-      break;
+      assert(union_type);
+      return Print<const void *>(val, *union_type, indent, nullptr, opts,
+                                 _text);
     case BASE_TYPE_STRUCT:
       if (!GenStruct(*type.struct_def,
                      reinterpret_cast<const Table *>(val),
@@ -236,7 +230,7 @@ template<typename T> static bool GenField(const FieldDef &fd,
 
 // Generate text for non-scalar field.
 static bool GenFieldOffset(const FieldDef &fd, const Table *table, bool fixed,
-                           int indent, StructDef *union_sd,
+                           int indent, Type *union_type,
                            const IDLOptions &opts, std::string *_text) {
   const void *val = nullptr;
   if (fixed) {
@@ -249,7 +243,7 @@ static bool GenFieldOffset(const FieldDef &fd, const Table *table, bool fixed,
       ? table->GetStruct<const void *>(fd.value.offset)
       : table->GetPointer<const void *>(fd.value.offset);
   }
-  return Print(val, fd.value.type, indent, union_sd, opts, _text);
+  return Print(val, fd.value.type, indent, union_type, opts, _text);
 }
 
 // Generate text for a struct or table, values separated by commas, indented,
@@ -260,7 +254,7 @@ static bool GenStruct(const StructDef &struct_def, const Table *table,
   std::string &text = *_text;
   text += "{";
   int fieldout = 0;
-  StructDef *union_sd = nullptr;
+  Type *union_type = nullptr;
   for (auto it = struct_def.fields.vec.begin();
        it != struct_def.fields.vec.end();
        ++it) {
@@ -296,7 +290,7 @@ static bool GenStruct(const StructDef &struct_def, const Table *table,
             FLATBUFFERS_GEN_TYPES_POINTER(FLATBUFFERS_TD)
           #undef FLATBUFFERS_TD
               if (!GenFieldOffset(fd, table, struct_def.fixed, indent + Indent(opts),
-                                  union_sd, opts, _text)) {
+                                  union_type, opts, _text)) {
                 return false;
               }
               break;
@@ -305,7 +299,7 @@ static bool GenStruct(const StructDef &struct_def, const Table *table,
           auto enum_val = fd.value.type.enum_def->ReverseLookup(
                                   table->GetField<uint8_t>(fd.value.offset, 0));
           assert(enum_val);
-          union_sd = enum_val->struct_def;
+          union_type = &enum_val->union_type;
         }
       }
       else

src/idl_parser.cpp

@@ -735,6 +735,13 @@ CheckedError Parser::ParseField(StructDef &struct_def) {
   return NoError();
 }
 
+CheckedError Parser::ParseString(Value &val) {
+  auto s = attribute_;
+  EXPECT(kTokenStringConstant);
+  val.constant = NumToString(builder_.CreateString(s).o);
+  return NoError();
+}
+
 CheckedError Parser::ParseAnyValue(Value &val, FieldDef *field,
                                    size_t parent_fieldn,
                                    const StructDef *parent_struct_def) {
@@ -784,16 +791,27 @@ CheckedError Parser::ParseAnyValue(Value &val, FieldDef *field,
       ECHECK(atot(constant.c_str(), *this, &enum_idx));
       auto enum_val = val.type.enum_def->ReverseLookup(enum_idx);
       if (!enum_val) return Error("illegal type id for: " + field->name);
-      ECHECK(ParseTable(*enum_val->struct_def, &val.constant, nullptr));
+      if (enum_val->union_type.base_type == BASE_TYPE_STRUCT) {
+        ECHECK(ParseTable(*enum_val->union_type.struct_def, &val.constant,
+                          nullptr));
+        if (enum_val->union_type.struct_def->fixed) {
+          // All BASE_TYPE_UNION values are offsets, so turn this into one.
+          SerializeStruct(*enum_val->union_type.struct_def, val);
+          builder_.ClearOffsets();
+          val.constant = NumToString(builder_.GetSize());
+        }
+      } else if (enum_val->union_type.base_type == BASE_TYPE_STRING) {
+        ECHECK(ParseString(val));
+      } else {
+        assert(false);
+      }
       break;
     }
     case BASE_TYPE_STRUCT:
       ECHECK(ParseTable(*val.type.struct_def, &val.constant, nullptr));
       break;
     case BASE_TYPE_STRING: {
-      auto s = attribute_;
-      EXPECT(kTokenStringConstant);
-      val.constant = NumToString(builder_.CreateString(s).o);
+      ECHECK(ParseString(val));
       break;
     }
     case BASE_TYPE_VECTOR: {
@@ -1290,7 +1308,16 @@ CheckedError Parser::ParseEnum(bool is_union, EnumDef **dest) {
         return Error("enum value already exists: " + value_name);
       ev.doc_comment = value_comment;
       if (is_union) {
-        ev.struct_def = LookupCreateStruct(full_name);
+        if (Is(':')) {
+          NEXT();
+          ECHECK(ParseType(ev.union_type));
+          if (ev.union_type.base_type != BASE_TYPE_STRUCT &&
+              ev.union_type.base_type != BASE_TYPE_STRING)
+            return Error("union value type may only be table/struct/string");
+          enum_def.uses_type_aliases = true;
+        } else {
+          ev.union_type = Type(BASE_TYPE_STRUCT, LookupCreateStruct(full_name));
+        }
       }
       if (Is('=')) {
         NEXT();
@@ -1994,6 +2021,8 @@ CheckedError Parser::DoParse(const char *source, const char **include_paths,
       return Error("type referenced but not defined: " + (*it)->name);
     }
   }
+  // This check has to happen here and not earlier, because only now do we
+  // know for sure what the type of these are.
   for (auto it = enums_.vec.begin(); it != enums_.vec.end(); ++it) {
     auto &enum_def = **it;
     if (enum_def.is_union) {
@@ -2001,8 +2030,11 @@ CheckedError Parser::DoParse(const char *source, const char **include_paths,
            val_it != enum_def.vals.vec.end();
            ++val_it) {
         auto &val = **val_it;
-        if (val.struct_def && val.struct_def->fixed)
-          return Error("only tables can be union elements: " + val.name);
+        if (opts.lang_to_generate != IDLOptions::kCpp &&
+            val.union_type.struct_def && val.union_type.struct_def->fixed)
+          return Error(
+                "only tables can be union elements in the generated language: "
+                + val.name);
       }
     }
   }
@@ -2145,9 +2177,11 @@ Offset<reflection::EnumVal> EnumVal::Serialize(FlatBufferBuilder *builder) const
   return reflection::CreateEnumVal(*builder,
                                    builder->CreateString(name),
                                    value,
-                                   struct_def
-                                     ? struct_def->serialized_location
-                                     : 0);
+                                   union_type.struct_def
+                                     ? union_type.struct_def->
+                                         serialized_location
+                                     : 0,
+                                   union_type.Serialize(builder));
 }
 
 Offset<reflection::Type> Type::Serialize(FlatBufferBuilder *builder) const {

tests/generate_code.sh

@@ -16,7 +16,7 @@
 
 ../flatc --cpp --java --csharp --go --binary --python --js --ts --php --grpc --gen-mutable --gen-object-api --no-includes monster_test.fbs monsterdata_test.json
 ../flatc --cpp --java --csharp --go --binary --python --js --ts --php --gen-mutable -o namespace_test namespace_test/namespace_test1.fbs namespace_test/namespace_test2.fbs
-../flatc --cpp -o union_vector ./union_vector/union_vector.fbs
+../flatc --cpp --gen-mutable --gen-object-api -o union_vector ./union_vector/union_vector.fbs
 ../flatc -b --schema --bfbs-comments monster_test.fbs
 cd ../samples
 ../flatc --cpp --gen-mutable --gen-object-api monster.fbs

tests/monster_test_generated.h

@@ -102,43 +102,43 @@ template<> struct AnyTraits<MyGame::Example2::Monster> {
 
 struct AnyUnion {
   Any type;
-  flatbuffers::NativeTable *table;
+  void *value;
 
-  AnyUnion() : type(Any_NONE), table(nullptr) {}
+  AnyUnion() : type(Any_NONE), value(nullptr) {}
   AnyUnion(AnyUnion&& u) FLATBUFFERS_NOEXCEPT :
-    type(Any_NONE), table(nullptr)
-    { std::swap(type, u.type); std::swap(table, u.table); }
+    type(Any_NONE), value(nullptr)
+    { std::swap(type, u.type); std::swap(value, u.value); }
   AnyUnion(const AnyUnion &);
   AnyUnion &operator=(const AnyUnion &);
   AnyUnion &operator=(AnyUnion &&u) FLATBUFFERS_NOEXCEPT
-    { std::swap(type, u.type); std::swap(table, u.table); return *this; }
+    { std::swap(type, u.type); std::swap(value, u.value); return *this; }
   ~AnyUnion() { Reset(); }
 
   void Reset();
 
   template <typename T>
-  void Set(T&& value) {
+  void Set(T&& val) {
     Reset();
     type = AnyTraits<typename T::TableType>::enum_value;
     if (type != Any_NONE) {
-      table = new T(std::forward<T>(value));
+      value = new T(std::forward<T>(val));
     }
   }
 
-  static flatbuffers::NativeTable *UnPack(const void *obj, Any type, const flatbuffers::resolver_function_t *resolver);
+  static void *UnPack(const void *obj, Any type, const flatbuffers::resolver_function_t *resolver);
   flatbuffers::Offset<void> Pack(flatbuffers::FlatBufferBuilder &_fbb, const flatbuffers::rehasher_function_t *_rehasher = nullptr) const;
 
   MonsterT *AsMonster() {
     return type == Any_Monster ?
-      reinterpret_cast<MonsterT *>(table) : nullptr;
+      reinterpret_cast<MonsterT *>(value) : nullptr;
   }
   TestSimpleTableWithEnumT *AsTestSimpleTableWithEnum() {
     return type == Any_TestSimpleTableWithEnum ?
-      reinterpret_cast<TestSimpleTableWithEnumT *>(table) : nullptr;
+      reinterpret_cast<TestSimpleTableWithEnumT *>(value) : nullptr;
   }
   MyGame::Example2::MonsterT *AsMyGame_Example2_Monster() {
     return type == Any_MyGame_Example2_Monster ?
-      reinterpret_cast<MyGame::Example2::MonsterT *>(table) : nullptr;
+      reinterpret_cast<MyGame::Example2::MonsterT *>(value) : nullptr;
   }
 };
 
@@ -629,13 +629,13 @@ struct Monster FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
   }
   template<typename T> const T *test_as() const;
   const Monster *test_as_Monster() const {
-    return (test_type() == Any_Monster)? static_cast<const Monster *>(test()) : nullptr;
+    return test_type() == Any_Monster ? static_cast<const Monster *>(test()) : nullptr;
   }
   const TestSimpleTableWithEnum *test_as_TestSimpleTableWithEnum() const {
-    return (test_type() == Any_TestSimpleTableWithEnum)? static_cast<const TestSimpleTableWithEnum *>(test()) : nullptr;
+    return test_type() == Any_TestSimpleTableWithEnum ? static_cast<const TestSimpleTableWithEnum *>(test()) : nullptr;
   }
   const MyGame::Example2::Monster *test_as_MyGame_Example2_Monster() const {
-    return (test_type() == Any_MyGame_Example2_Monster)? static_cast<const MyGame::Example2::Monster *>(test()) : nullptr;
+    return test_type() == Any_MyGame_Example2_Monster ? static_cast<const MyGame::Example2::Monster *>(test()) : nullptr;
   }
   void *mutable_test() {
     return GetPointer<void *>(VT_TEST);
@@ -1172,7 +1172,7 @@ inline void Monster::UnPackTo(MonsterT *_o, const flatbuffers::resolver_function
   { auto _e = inventory(); if (_e) { _o->inventory.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->inventory[_i] = _e->Get(_i); } } };
   { auto _e = color(); _o->color = _e; };
   { auto _e = test_type(); _o->test.type = _e; };
-  { auto _e = test(); if (_e) _o->test.table = AnyUnion::UnPack(_e, test_type(),_resolver); };
+  { auto _e = test(); if (_e) _o->test.value = AnyUnion::UnPack(_e, test_type(), _resolver); };
   { auto _e = test4(); if (_e) { _o->test4.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->test4[_i] = *_e->Get(_i); } } };
   { auto _e = testarrayofstring(); if (_e) { _o->testarrayofstring.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->testarrayofstring[_i] = _e->Get(_i)->str(); } } };
   { auto _e = testarrayoftables(); if (_e) { _o->testarrayoftables.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->testarrayoftables[_i] = std::unique_ptr<MonsterT>(_e->Get(_i)->UnPack(_resolver)); } } };
@@ -1297,7 +1297,7 @@ inline bool VerifyAnyVector(flatbuffers::Verifier &verifier, const flatbuffers::
   return true;
 }
 
-inline flatbuffers::NativeTable *AnyUnion::UnPack(const void *obj, Any type, const flatbuffers::resolver_function_t *resolver) {
+inline void *AnyUnion::UnPack(const void *obj, Any type, const flatbuffers::resolver_function_t *resolver) {
   switch (type) {
     case Any_Monster: {
       auto ptr = reinterpret_cast<const Monster *>(obj);
@@ -1318,15 +1318,15 @@ inline flatbuffers::NativeTable *AnyUnion::UnPack(const void *obj, Any type, con
 inline flatbuffers::Offset<void> AnyUnion::Pack(flatbuffers::FlatBufferBuilder &_fbb, const flatbuffers::rehasher_function_t *_rehasher) const {
   switch (type) {
     case Any_Monster: {
-      auto ptr = reinterpret_cast<const MonsterT *>(table);
+      auto ptr = reinterpret_cast<const MonsterT *>(value);
       return CreateMonster(_fbb, ptr, _rehasher).Union();
     }
     case Any_TestSimpleTableWithEnum: {
-      auto ptr = reinterpret_cast<const TestSimpleTableWithEnumT *>(table);
+      auto ptr = reinterpret_cast<const TestSimpleTableWithEnumT *>(value);
       return CreateTestSimpleTableWithEnum(_fbb, ptr, _rehasher).Union();
     }
     case Any_MyGame_Example2_Monster: {
-      auto ptr = reinterpret_cast<const MyGame::Example2::MonsterT *>(table);
+      auto ptr = reinterpret_cast<const MyGame::Example2::MonsterT *>(value);
       return CreateMonster(_fbb, ptr, _rehasher).Union();
     }
     default: return 0;
@@ -1336,23 +1336,23 @@ inline flatbuffers::Offset<void> AnyUnion::Pack(flatbuffers::FlatBufferBuilder &
 inline void AnyUnion::Reset() {
   switch (type) {
     case Any_Monster: {
-      auto ptr = reinterpret_cast<MonsterT *>(table);
+      auto ptr = reinterpret_cast<MonsterT *>(value);
       delete ptr;
       break;
     }
     case Any_TestSimpleTableWithEnum: {
-      auto ptr = reinterpret_cast<TestSimpleTableWithEnumT *>(table);
+      auto ptr = reinterpret_cast<TestSimpleTableWithEnumT *>(value);
       delete ptr;
       break;
     }
     case Any_MyGame_Example2_Monster: {
-      auto ptr = reinterpret_cast<MyGame::Example2::MonsterT *>(table);
+      auto ptr = reinterpret_cast<MyGame::Example2::MonsterT *>(value);
       delete ptr;
       break;
     }
     default: break;
   }
-  table = nullptr;
+  value = nullptr;
   type = Any_NONE;
 }
 

tests/test.cpp

@@ -1334,46 +1334,78 @@ void UnionVectorTest() {
   // union types.
   std::vector<uint8_t> types;
   types.push_back(static_cast<uint8_t>(Character_Belle));
-  types.push_back(static_cast<uint8_t>(Character_Rapunzel));
   types.push_back(static_cast<uint8_t>(Character_MuLan));
+  types.push_back(static_cast<uint8_t>(Character_BookFan));
+  types.push_back(static_cast<uint8_t>(Character_Other));
+  types.push_back(static_cast<uint8_t>(Character_Unused));
 
   // union values.
   std::vector<flatbuffers::Offset<void>> characters;
-  characters.push_back(CreateBelle(fbb, /*books_read=*/7).Union());
-  characters.push_back(CreateRapunzel(fbb, /*hair_length=*/6).Union());
-  characters.push_back(CreateMuLan(fbb, /*sword_attack_damage=*/5).Union());
+  characters.push_back(fbb.CreateStruct(BookReader(/*books_read=*/7)).Union());
+  characters.push_back(CreateAttacker(fbb, /*sword_attack_damage=*/5).Union());
+  characters.push_back(fbb.CreateStruct(BookReader(/*books_read=*/2)).Union());
+  characters.push_back(fbb.CreateString("Other").Union());
+  characters.push_back(fbb.CreateString("Unused").Union());
 
   // create Movie.
   const auto movie_offset =
-      CreateMovie(fbb, fbb.CreateVector(types), fbb.CreateVector(characters));
+      CreateMovie(fbb,
+                  Character_Rapunzel,
+                  fbb.CreateStruct(Rapunzel(/*hair_length=*/6)).Union(),
+                  fbb.CreateVector(types),
+                  fbb.CreateVector(characters));
   FinishMovieBuffer(fbb, movie_offset);
-  uint8_t *buf = fbb.GetBufferPointer();
+  auto buf = fbb.GetBufferPointer();
 
   flatbuffers::Verifier verifier(buf, fbb.GetSize());
   TEST_EQ(VerifyMovieBuffer(verifier), true);
 
-  const Movie *movie = GetMovie(buf);
-  TEST_EQ(movie->characters_type()->size(), 3);
-  TEST_EQ(
-      movie->characters_type()->GetEnum<Character>(0) == Character_Belle,
-      true);
-  TEST_EQ(
-      movie->characters_type()->GetEnum<Character>(1) == Character_Rapunzel,
-      true);
-  TEST_EQ(
-      movie->characters_type()->GetEnum<Character>(2) == Character_MuLan,
-      true);
+  auto flat_movie = GetMovie(buf);
 
-  TEST_EQ(movie->characters()->size(), 3);
-  const Belle *belle =
-      reinterpret_cast<const Belle*>(movie->characters()->Get(0));
-  TEST_EQ(belle->books_read(), 7);
-  const Rapunzel *rapunzel =
-      reinterpret_cast<const Rapunzel*>(movie->characters()->Get(1));
+  auto TestMovie = [](const Movie *movie) {
+    TEST_EQ(movie->main_character_type() == Character_Rapunzel, true);
+
+    auto cts = movie->characters_type();
+    TEST_EQ(movie->characters_type()->size(), 5);
+    TEST_EQ(cts->GetEnum<Character>(0) == Character_Belle, true);
+    TEST_EQ(cts->GetEnum<Character>(1) == Character_MuLan, true);
+    TEST_EQ(cts->GetEnum<Character>(2) == Character_BookFan, true);
+    TEST_EQ(cts->GetEnum<Character>(3) == Character_Other, true);
+    TEST_EQ(cts->GetEnum<Character>(4) == Character_Unused, true);
+
+    auto rapunzel = movie->main_character_as_Rapunzel();
     TEST_EQ(rapunzel->hair_length(), 6);
-  const MuLan *mu_lan =
-      reinterpret_cast<const MuLan*>(movie->characters()->Get(2));
+
+    auto cs = movie->characters();
+    TEST_EQ(cs->size(), 5);
+    auto belle = cs->GetAs<BookReader>(0);
+    TEST_EQ(belle->books_read(), 7);
+    auto mu_lan = cs->GetAs<Attacker>(1);
     TEST_EQ(mu_lan->sword_attack_damage(), 5);
+    auto book_fan = cs->GetAs<BookReader>(2);
+    TEST_EQ(book_fan->books_read(), 2);
+    auto other = cs->GetAsString(3);
+    TEST_EQ_STR(other->c_str(), "Other");
+    auto unused = cs->GetAsString(4);
+    TEST_EQ_STR(unused->c_str(), "Unused");
+  };
+
+  TestMovie(flat_movie);
+
+  auto movie_object = flat_movie->UnPack();
+  TEST_EQ(movie_object->main_character.AsRapunzel()->hair_length(), 6);
+  TEST_EQ(movie_object->characters[0].AsBelle()->books_read(), 7);
+  TEST_EQ(movie_object->characters[1].AsMuLan()->sword_attack_damage, 5);
+  TEST_EQ(movie_object->characters[2].AsBookFan()->books_read(), 2);
+  TEST_EQ_STR(movie_object->characters[3].AsOther()->c_str(), "Other");
+  TEST_EQ_STR(movie_object->characters[4].AsUnused()->c_str(), "Unused");
+
+  fbb.Clear();
+  fbb.Finish(Movie::Pack(fbb, movie_object));
+
+  auto repacked_movie = GetMovie(fbb.GetBufferPointer());
+
+  TestMovie(repacked_movie);
 }
 
 void ConformTest() {

tests/union_vector/union_vector.fbs

-table MuLan {
+// Demonstrates the ability to have vectors of unions, and also to
+// store structs and strings in unions.
+
+table Attacker {
   sword_attack_damage: int;
 }
 
-table Rapunzel {
+struct Rapunzel {
   hair_length: int;
 }
 
-table Belle {
+struct BookReader {
   books_read: int;
 }
 
 union Character {
-  MuLan,
-  Rapunzel,
-  Belle,
+  MuLan: Attacker,  // Can have name be different from type.
+  Rapunzel,         // Or just both the same, as before.
+  Belle: BookReader,
+  BookFan: BookReader,
+  Other: string,
+  Unused: string
 }
 
 table Movie {
+  main_character: Character;
   characters: [Character];
 }
 

tests/union_vector/union_vector_generated.h

@@ -6,21 +6,26 @@
 
 #include "flatbuffers/flatbuffers.h"
 
-struct MuLan;
+struct Attacker;
+struct AttackerT;
 
 struct Rapunzel;
 
-struct Belle;
+struct BookReader;
 
 struct Movie;
+struct MovieT;
 
 enum Character {
   Character_NONE = 0,
   Character_MuLan = 1,
   Character_Rapunzel = 2,
   Character_Belle = 3,
+  Character_BookFan = 4,
+  Character_Other = 5,
+  Character_Unused = 6,
   Character_MIN = Character_NONE,
-  Character_MAX = Character_Belle
+  Character_MAX = Character_Unused
 };
 
 inline const char **EnumNamesCharacter() {
@@ -29,6 +34,9 @@ inline const char **EnumNamesCharacter() {
     "MuLan",
     "Rapunzel",
     "Belle",
+    "BookFan",
+    "Other",
+    "Unused",
     nullptr
   };
   return names;
@@ -39,158 +47,221 @@ inline const char *EnumNameCharacter(Character e) {
   return EnumNamesCharacter()[index];
 }
 
-template<typename T> struct CharacterTraits {
-  static const Character enum_value = Character_NONE;
-};
+struct CharacterUnion {
+  Character type;
+  void *value;
 
-template<> struct CharacterTraits<MuLan> {
-  static const Character enum_value = Character_MuLan;
-};
+  CharacterUnion() : type(Character_NONE), value(nullptr) {}
+  CharacterUnion(CharacterUnion&& u) FLATBUFFERS_NOEXCEPT :
+    type(Character_NONE), value(nullptr)
+    { std::swap(type, u.type); std::swap(value, u.value); }
+  CharacterUnion(const CharacterUnion &);
+  CharacterUnion &operator=(const CharacterUnion &);
+  CharacterUnion &operator=(CharacterUnion &&u) FLATBUFFERS_NOEXCEPT
+    { std::swap(type, u.type); std::swap(value, u.value); return *this; }
+  ~CharacterUnion() { Reset(); }
 
-template<> struct CharacterTraits<Rapunzel> {
-  static const Character enum_value = Character_Rapunzel;
-};
+  void Reset();
 
-template<> struct CharacterTraits<Belle> {
-  static const Character enum_value = Character_Belle;
+  static void *UnPack(const void *obj, Character type, const flatbuffers::resolver_function_t *resolver);
+  flatbuffers::Offset<void> Pack(flatbuffers::FlatBufferBuilder &_fbb, const flatbuffers::rehasher_function_t *_rehasher = nullptr) const;
+
+  AttackerT *AsMuLan() {
+    return type == Character_MuLan ?
+      reinterpret_cast<AttackerT *>(value) : nullptr;
+  }
+  Rapunzel *AsRapunzel() {
+    return type == Character_Rapunzel ?
+      reinterpret_cast<Rapunzel *>(value) : nullptr;
+  }
+  BookReader *AsBelle() {
+    return type == Character_Belle ?
+      reinterpret_cast<BookReader *>(value) : nullptr;
+  }
+  BookReader *AsBookFan() {
+    return type == Character_BookFan ?
+      reinterpret_cast<BookReader *>(value) : nullptr;
+  }
+  std::string *AsOther() {
+    return type == Character_Other ?
+      reinterpret_cast<std::string *>(value) : nullptr;
+  }
+  std::string *AsUnused() {
+    return type == Character_Unused ?
+      reinterpret_cast<std::string *>(value) : nullptr;
+  }
 };
 
 bool VerifyCharacter(flatbuffers::Verifier &verifier, const void *obj, Character type);
 bool VerifyCharacterVector(flatbuffers::Verifier &verifier, const flatbuffers::Vector<flatbuffers::Offset<void>> *values, const flatbuffers::Vector<uint8_t> *types);
 
-struct MuLan FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
-  enum {
-    VT_SWORD_ATTACK_DAMAGE = 4
-  };
-  int32_t sword_attack_damage() const {
-    return GetField<int32_t>(VT_SWORD_ATTACK_DAMAGE, 0);
+MANUALLY_ALIGNED_STRUCT(4) Rapunzel FLATBUFFERS_FINAL_CLASS {
+ private:
+  int32_t hair_length_;
+
+ public:
+  Rapunzel() {
+    memset(this, 0, sizeof(Rapunzel));
   }
-  bool Verify(flatbuffers::Verifier &verifier) const {
-    return VerifyTableStart(verifier) &&
-           VerifyField<int32_t>(verifier, VT_SWORD_ATTACK_DAMAGE) &&
-           verifier.EndTable();
+  Rapunzel(const Rapunzel &_o) {
+    memcpy(this, &_o, sizeof(Rapunzel));
   }
-};
-
-struct MuLanBuilder {
-  flatbuffers::FlatBufferBuilder &fbb_;
-  flatbuffers::uoffset_t start_;
-  void add_sword_attack_damage(int32_t sword_attack_damage) {
-    fbb_.AddElement<int32_t>(MuLan::VT_SWORD_ATTACK_DAMAGE, sword_attack_damage, 0);
+  Rapunzel(int32_t _hair_length)
+      : hair_length_(flatbuffers::EndianScalar(_hair_length)) {
   }
-  MuLanBuilder(flatbuffers::FlatBufferBuilder &_fbb)
-        : fbb_(_fbb) {
-    start_ = fbb_.StartTable();
+  int32_t hair_length() const {
+    return flatbuffers::EndianScalar(hair_length_);
   }
-  MuLanBuilder &operator=(const MuLanBuilder &);
-  flatbuffers::Offset<MuLan> Finish() {
-    const auto end = fbb_.EndTable(start_, 1);
-    auto o = flatbuffers::Offset<MuLan>(end);
-    return o;
+  void mutate_hair_length(int32_t _hair_length) {
+    flatbuffers::WriteScalar(&hair_length_, _hair_length);
   }
 };
+STRUCT_END(Rapunzel, 4);
 
-inline flatbuffers::Offset<MuLan> CreateMuLan(
-    flatbuffers::FlatBufferBuilder &_fbb,
-    int32_t sword_attack_damage = 0) {
-  MuLanBuilder builder_(_fbb);
-  builder_.add_sword_attack_damage(sword_attack_damage);
-  return builder_.Finish();
-}
+MANUALLY_ALIGNED_STRUCT(4) BookReader FLATBUFFERS_FINAL_CLASS {
+ private:
+  int32_t books_read_;
 
-struct Rapunzel FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
-  enum {
-    VT_HAIR_LENGTH = 4
-  };
-  int32_t hair_length() const {
-    return GetField<int32_t>(VT_HAIR_LENGTH, 0);
+ public:
+  BookReader() {
+    memset(this, 0, sizeof(BookReader));
   }
-  bool Verify(flatbuffers::Verifier &verifier) const {
-    return VerifyTableStart(verifier) &&
-           VerifyField<int32_t>(verifier, VT_HAIR_LENGTH) &&
-           verifier.EndTable();
+  BookReader(const BookReader &_o) {
+    memcpy(this, &_o, sizeof(BookReader));
   }
-};
-
-struct RapunzelBuilder {
-  flatbuffers::FlatBufferBuilder &fbb_;
-  flatbuffers::uoffset_t start_;
-  void add_hair_length(int32_t hair_length) {
-    fbb_.AddElement<int32_t>(Rapunzel::VT_HAIR_LENGTH, hair_length, 0);
+  BookReader(int32_t _books_read)
+      : books_read_(flatbuffers::EndianScalar(_books_read)) {
   }
-  RapunzelBuilder(flatbuffers::FlatBufferBuilder &_fbb)
-        : fbb_(_fbb) {
-    start_ = fbb_.StartTable();
+  int32_t books_read() const {
+    return flatbuffers::EndianScalar(books_read_);
   }
-  RapunzelBuilder &operator=(const RapunzelBuilder &);
-  flatbuffers::Offset<Rapunzel> Finish() {
-    const auto end = fbb_.EndTable(start_, 1);
-    auto o = flatbuffers::Offset<Rapunzel>(end);
-    return o;
+  void mutate_books_read(int32_t _books_read) {
+    flatbuffers::WriteScalar(&books_read_, _books_read);
   }
 };
+STRUCT_END(BookReader, 4);
 
-inline flatbuffers::Offset<Rapunzel> CreateRapunzel(
-    flatbuffers::FlatBufferBuilder &_fbb,
-    int32_t hair_length = 0) {
-  RapunzelBuilder builder_(_fbb);
-  builder_.add_hair_length(hair_length);
-  return builder_.Finish();
-}
+struct AttackerT : public flatbuffers::NativeTable {
+  typedef Attacker TableType;
+  int32_t sword_attack_damage;
+  AttackerT()
+      : sword_attack_damage(0) {
+  }
+};
 
-struct Belle FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
+struct Attacker FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
+  typedef AttackerT NativeTableType;
   enum {
-    VT_BOOKS_READ = 4
+    VT_SWORD_ATTACK_DAMAGE = 4
   };
-  int32_t books_read() const {
-    return GetField<int32_t>(VT_BOOKS_READ, 0);
+  int32_t sword_attack_damage() const {
+    return GetField<int32_t>(VT_SWORD_ATTACK_DAMAGE, 0);
+  }
+  bool mutate_sword_attack_damage(int32_t _sword_attack_damage) {
+    return SetField<int32_t>(VT_SWORD_ATTACK_DAMAGE, _sword_attack_damage, 0);
   }
   bool Verify(flatbuffers::Verifier &verifier) const {
     return VerifyTableStart(verifier) &&
-           VerifyField<int32_t>(verifier, VT_BOOKS_READ) &&
+           VerifyField<int32_t>(verifier, VT_SWORD_ATTACK_DAMAGE) &&
            verifier.EndTable();
   }
+  AttackerT *UnPack(const flatbuffers::resolver_function_t *_resolver = nullptr) const;
+  void UnPackTo(AttackerT *_o, const flatbuffers::resolver_function_t *_resolver = nullptr) const;
+  static flatbuffers::Offset<Attacker> Pack(flatbuffers::FlatBufferBuilder &_fbb, const AttackerT* _o, const flatbuffers::rehasher_function_t *_rehasher = nullptr);
 };
 
-struct BelleBuilder {
+struct AttackerBuilder {
   flatbuffers::FlatBufferBuilder &fbb_;
   flatbuffers::uoffset_t start_;
-  void add_books_read(int32_t books_read) {
-    fbb_.AddElement<int32_t>(Belle::VT_BOOKS_READ, books_read, 0);
+  void add_sword_attack_damage(int32_t sword_attack_damage) {
+    fbb_.AddElement<int32_t>(Attacker::VT_SWORD_ATTACK_DAMAGE, sword_attack_damage, 0);
   }
-  BelleBuilder(flatbuffers::FlatBufferBuilder &_fbb)
+  AttackerBuilder(flatbuffers::FlatBufferBuilder &_fbb)
         : fbb_(_fbb) {
     start_ = fbb_.StartTable();
   }
-  BelleBuilder &operator=(const BelleBuilder &);
-  flatbuffers::Offset<Belle> Finish() {
+  AttackerBuilder &operator=(const AttackerBuilder &);
+  flatbuffers::Offset<Attacker> Finish() {
     const auto end = fbb_.EndTable(start_, 1);
-    auto o = flatbuffers::Offset<Belle>(end);
+    auto o = flatbuffers::Offset<Attacker>(end);
     return o;
   }
 };
 
-inline flatbuffers::Offset<Belle> CreateBelle(
+inline flatbuffers::Offset<Attacker> CreateAttacker(
     flatbuffers::FlatBufferBuilder &_fbb,
-    int32_t books_read = 0) {
-  BelleBuilder builder_(_fbb);
-  builder_.add_books_read(books_read);
+    int32_t sword_attack_damage = 0) {
+  AttackerBuilder builder_(_fbb);
+  builder_.add_sword_attack_damage(sword_attack_damage);
   return builder_.Finish();
 }
 
+flatbuffers::Offset<Attacker> CreateAttacker(flatbuffers::FlatBufferBuilder &_fbb, const AttackerT *_o, const flatbuffers::rehasher_function_t *_rehasher = nullptr);
+
+struct MovieT : public flatbuffers::NativeTable {
+  typedef Movie TableType;
+  CharacterUnion main_character;
+  std::vector<CharacterUnion> characters;
+  MovieT() {
+  }
+};
+
 struct Movie FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
+  typedef MovieT NativeTableType;
   enum {
-    VT_CHARACTERS_TYPE = 4,
-    VT_CHARACTERS = 6
+    VT_MAIN_CHARACTER_TYPE = 4,
+    VT_MAIN_CHARACTER = 6,
+    VT_CHARACTERS_TYPE = 8,
+    VT_CHARACTERS = 10
   };
+  Character main_character_type() const {
+    return static_cast<Character>(GetField<uint8_t>(VT_MAIN_CHARACTER_TYPE, 0));
+  }
+  bool mutate_main_character_type(Character _main_character_type) {
+    return SetField<uint8_t>(VT_MAIN_CHARACTER_TYPE, static_cast<uint8_t>(_main_character_type), 0);
+  }
+  const void *main_character() const {
+    return GetPointer<const void *>(VT_MAIN_CHARACTER);
+  }
+  template<typename T> const T *main_character_as() const;
+  const Attacker *main_character_as_MuLan() const {
+    return main_character_type() == Character_MuLan ? static_cast<const Attacker *>(main_character()) : nullptr;
+  }
+  const Rapunzel *main_character_as_Rapunzel() const {
+    return main_character_type() == Character_Rapunzel ? static_cast<const Rapunzel *>(main_character()) : nullptr;
+  }
+  const BookReader *main_character_as_Belle() const {
+    return main_character_type() == Character_Belle ? static_cast<const BookReader *>(main_character()) : nullptr;
+  }
+  const BookReader *main_character_as_BookFan() const {
+    return main_character_type() == Character_BookFan ? static_cast<const BookReader *>(main_character()) : nullptr;
+  }
+  const flatbuffers::String *main_character_as_Other() const {
+    return main_character_type() == Character_Other ? static_cast<const flatbuffers::String *>(main_character()) : nullptr;
+  }
+  const flatbuffers::String *main_character_as_Unused() const {
+    return main_character_type() == Character_Unused ? static_cast<const flatbuffers::String *>(main_character()) : nullptr;
+  }
+  void *mutable_main_character() {
+    return GetPointer<void *>(VT_MAIN_CHARACTER);
+  }
   const flatbuffers::Vector<uint8_t> *characters_type() const {
     return GetPointer<const flatbuffers::Vector<uint8_t> *>(VT_CHARACTERS_TYPE);
   }
+  flatbuffers::Vector<uint8_t> *mutable_characters_type() {
+    return GetPointer<flatbuffers::Vector<uint8_t> *>(VT_CHARACTERS_TYPE);
+  }
   const flatbuffers::Vector<flatbuffers::Offset<void>> *characters() const {
     return GetPointer<const flatbuffers::Vector<flatbuffers::Offset<void>> *>(VT_CHARACTERS);
   }
+  flatbuffers::Vector<flatbuffers::Offset<void>> *mutable_characters() {
+    return GetPointer<flatbuffers::Vector<flatbuffers::Offset<void>> *>(VT_CHARACTERS);
+  }
   bool Verify(flatbuffers::Verifier &verifier) const {
     return VerifyTableStart(verifier) &&
+           VerifyField<uint8_t>(verifier, VT_MAIN_CHARACTER_TYPE) &&
+           VerifyField<flatbuffers::uoffset_t>(verifier, VT_MAIN_CHARACTER) &&
+           VerifyCharacter(verifier, main_character(), main_character_type()) &&
            VerifyField<flatbuffers::uoffset_t>(verifier, VT_CHARACTERS_TYPE) &&
            verifier.Verify(characters_type()) &&
            VerifyField<flatbuffers::uoffset_t>(verifier, VT_CHARACTERS) &&
@@ -198,11 +269,20 @@ struct Movie FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
            VerifyCharacterVector(verifier, characters(), characters_type()) &&
            verifier.EndTable();
   }
+  MovieT *UnPack(const flatbuffers::resolver_function_t *_resolver = nullptr) const;
+  void UnPackTo(MovieT *_o, const flatbuffers::resolver_function_t *_resolver = nullptr) const;
+  static flatbuffers::Offset<Movie> Pack(flatbuffers::FlatBufferBuilder &_fbb, const MovieT* _o, const flatbuffers::rehasher_function_t *_rehasher = nullptr);
 };
 
 struct MovieBuilder {
   flatbuffers::FlatBufferBuilder &fbb_;
   flatbuffers::uoffset_t start_;
+  void add_main_character_type(Character main_character_type) {
+    fbb_.AddElement<uint8_t>(Movie::VT_MAIN_CHARACTER_TYPE, static_cast<uint8_t>(main_character_type), 0);
+  }
+  void add_main_character(flatbuffers::Offset<void> main_character) {
+    fbb_.AddOffset(Movie::VT_MAIN_CHARACTER, main_character);
+  }
   void add_characters_type(flatbuffers::Offset<flatbuffers::Vector<uint8_t>> characters_type) {
     fbb_.AddOffset(Movie::VT_CHARACTERS_TYPE, characters_type);
   }
@@ -215,7 +295,7 @@ struct MovieBuilder {
   }
   MovieBuilder &operator=(const MovieBuilder &);
   flatbuffers::Offset<Movie> Finish() {
-    const auto end = fbb_.EndTable(start_, 2);
+    const auto end = fbb_.EndTable(start_, 4);
     auto o = flatbuffers::Offset<Movie>(end);
     return o;
   }
@@ -223,40 +303,118 @@ struct MovieBuilder {
 
 inline flatbuffers::Offset<Movie> CreateMovie(
     flatbuffers::FlatBufferBuilder &_fbb,
+    Character main_character_type = Character_NONE,
+    flatbuffers::Offset<void> main_character = 0,
     flatbuffers::Offset<flatbuffers::Vector<uint8_t>> characters_type = 0,
     flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<void>>> characters = 0) {
   MovieBuilder builder_(_fbb);
   builder_.add_characters(characters);
   builder_.add_characters_type(characters_type);
+  builder_.add_main_character(main_character);
+  builder_.add_main_character_type(main_character_type);
   return builder_.Finish();
 }
 
 inline flatbuffers::Offset<Movie> CreateMovieDirect(
     flatbuffers::FlatBufferBuilder &_fbb,
+    Character main_character_type = Character_NONE,
+    flatbuffers::Offset<void> main_character = 0,
     const std::vector<uint8_t> *characters_type = nullptr,
     const std::vector<flatbuffers::Offset<void>> *characters = nullptr) {
   return CreateMovie(
       _fbb,
+      main_character_type,
+      main_character,
       characters_type ? _fbb.CreateVector<uint8_t>(*characters_type) : 0,
       characters ? _fbb.CreateVector<flatbuffers::Offset<void>>(*characters) : 0);
 }
 
+flatbuffers::Offset<Movie> CreateMovie(flatbuffers::FlatBufferBuilder &_fbb, const MovieT *_o, const flatbuffers::rehasher_function_t *_rehasher = nullptr);
+
+inline AttackerT *Attacker::UnPack(const flatbuffers::resolver_function_t *_resolver) const {
+  auto _o = new AttackerT();
+  UnPackTo(_o, _resolver);
+  return _o;
+}
+
+inline void Attacker::UnPackTo(AttackerT *_o, const flatbuffers::resolver_function_t *_resolver) const {
+  (void)_o;
+  (void)_resolver;
+  { auto _e = sword_attack_damage(); _o->sword_attack_damage = _e; };
+}
+
+inline flatbuffers::Offset<Attacker> Attacker::Pack(flatbuffers::FlatBufferBuilder &_fbb, const AttackerT* _o, const flatbuffers::rehasher_function_t *_rehasher) {
+  return CreateAttacker(_fbb, _o, _rehasher);
+}
+
+inline flatbuffers::Offset<Attacker> CreateAttacker(flatbuffers::FlatBufferBuilder &_fbb, const AttackerT *_o, const flatbuffers::rehasher_function_t *_rehasher) {
+  (void)_rehasher;
+  (void)_o;
+  auto _sword_attack_damage = _o->sword_attack_damage;
+  return CreateAttacker(
+      _fbb,
+      _sword_attack_damage);
+}
+
+inline MovieT *Movie::UnPack(const flatbuffers::resolver_function_t *_resolver) const {
+  auto _o = new MovieT();
+  UnPackTo(_o, _resolver);
+  return _o;
+}
+
+inline void Movie::UnPackTo(MovieT *_o, const flatbuffers::resolver_function_t *_resolver) const {
+  (void)_o;
+  (void)_resolver;
+  { auto _e = main_character_type(); _o->main_character.type = _e; };
+  { auto _e = main_character(); if (_e) _o->main_character.value = CharacterUnion::UnPack(_e, main_character_type(), _resolver); };
+  { auto _e = characters_type(); if (_e) { _o->characters.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->characters[_i].type = (Character)_e->Get(_i); } } };
+  { auto _e = characters(); if (_e) { _o->characters.resize(_e->size()); for (flatbuffers::uoffset_t _i = 0; _i < _e->size(); _i++) { _o->characters[_i].value = CharacterUnion::UnPack(_e->Get(_i), characters_type()->GetEnum<Character>(_i), _resolver); } } };
+}
+
+inline flatbuffers::Offset<Movie> Movie::Pack(flatbuffers::FlatBufferBuilder &_fbb, const MovieT* _o, const flatbuffers::rehasher_function_t *_rehasher) {
+  return CreateMovie(_fbb, _o, _rehasher);
+}
+
+inline flatbuffers::Offset<Movie> CreateMovie(flatbuffers::FlatBufferBuilder &_fbb, const MovieT *_o, const flatbuffers::rehasher_function_t *_rehasher) {
+  (void)_rehasher;
+  (void)_o;
+  auto _main_character_type = _o->main_character.type;
+  auto _main_character = _o->main_character.Pack(_fbb);
+  auto _characters_type = _o->characters.size() ? _fbb.CreateVector<uint8_t>(_o->characters.size(), [&](size_t i) { return static_cast<uint8_t>(_o->characters[i].type); }) : 0;
+  auto _characters = _o->characters.size() ? _fbb.CreateVector<flatbuffers::Offset<void>>(_o->characters.size(), [&](size_t i) { return _o->characters[i].Pack(_fbb, _rehasher); }) : 0;
+  return CreateMovie(
+      _fbb,
+      _main_character_type,
+      _main_character,
+      _characters_type,
+      _characters);
+}
+
 inline bool VerifyCharacter(flatbuffers::Verifier &verifier, const void *obj, Character type) {
   switch (type) {
     case Character_NONE: {
       return true;
     }
     case Character_MuLan: {
-      auto ptr = reinterpret_cast<const MuLan *>(obj);
+      auto ptr = reinterpret_cast<const Attacker *>(obj);
       return verifier.VerifyTable(ptr);
     }
     case Character_Rapunzel: {
-      auto ptr = reinterpret_cast<const Rapunzel *>(obj);
-      return verifier.VerifyTable(ptr);
+      return true;
     }
     case Character_Belle: {
-      auto ptr = reinterpret_cast<const Belle *>(obj);
-      return verifier.VerifyTable(ptr);
+      return true;
+    }
+    case Character_BookFan: {
+      return true;
+    }
+    case Character_Other: {
+      auto ptr = reinterpret_cast<const flatbuffers::String *>(obj);
+      return verifier.Verify(ptr);
+    }
+    case Character_Unused: {
+      auto ptr = reinterpret_cast<const flatbuffers::String *>(obj);
+      return verifier.Verify(ptr);
     }
     default: return false;
   }
@@ -273,10 +431,112 @@ inline bool VerifyCharacterVector(flatbuffers::Verifier &verifier, const flatbuf
   return true;
 }
 
+inline void *CharacterUnion::UnPack(const void *obj, Character type, const flatbuffers::resolver_function_t *resolver) {
+  switch (type) {
+    case Character_MuLan: {
+      auto ptr = reinterpret_cast<const Attacker *>(obj);
+      return ptr->UnPack(resolver);
+    }
+    case Character_Rapunzel: {
+      auto ptr = reinterpret_cast<const Rapunzel *>(obj);
+      return new Rapunzel(*ptr);
+    }
+    case Character_Belle: {
+      auto ptr = reinterpret_cast<const BookReader *>(obj);
+      return new BookReader(*ptr);
+    }
+    case Character_BookFan: {
+      auto ptr = reinterpret_cast<const BookReader *>(obj);
+      return new BookReader(*ptr);
+    }
+    case Character_Other: {
+      auto ptr = reinterpret_cast<const flatbuffers::String *>(obj);
+      return new std::string(ptr->c_str(), ptr->size());
+    }
+    case Character_Unused: {
+      auto ptr = reinterpret_cast<const flatbuffers::String *>(obj);
+      return new std::string(ptr->c_str(), ptr->size());
+    }
+    default: return nullptr;
+  }
+}
+
+inline flatbuffers::Offset<void> CharacterUnion::Pack(flatbuffers::FlatBufferBuilder &_fbb, const flatbuffers::rehasher_function_t *_rehasher) const {
+  switch (type) {
+    case Character_MuLan: {
+      auto ptr = reinterpret_cast<const AttackerT *>(value);
+      return CreateAttacker(_fbb, ptr, _rehasher).Union();
+    }
+    case Character_Rapunzel: {
+      auto ptr = reinterpret_cast<const Rapunzel *>(value);
+      return _fbb.CreateStruct(*ptr).Union();
+    }
+    case Character_Belle: {
+      auto ptr = reinterpret_cast<const BookReader *>(value);
+      return _fbb.CreateStruct(*ptr).Union();
+    }
+    case Character_BookFan: {
+      auto ptr = reinterpret_cast<const BookReader *>(value);
+      return _fbb.CreateStruct(*ptr).Union();
+    }
+    case Character_Other: {
+      auto ptr = reinterpret_cast<const std::string *>(value);
+      return _fbb.CreateString(*ptr).Union();
+    }
+    case Character_Unused: {
+      auto ptr = reinterpret_cast<const std::string *>(value);
+      return _fbb.CreateString(*ptr).Union();
+    }
+    default: return 0;
+  }
+}
+
+inline void CharacterUnion::Reset() {
+  switch (type) {
+    case Character_MuLan: {
+      auto ptr = reinterpret_cast<AttackerT *>(value);
+      delete ptr;
+      break;
+    }
+    case Character_Rapunzel: {
+      auto ptr = reinterpret_cast<Rapunzel *>(value);
+      delete ptr;
+      break;
+    }
+    case Character_Belle: {
+      auto ptr = reinterpret_cast<BookReader *>(value);
+      delete ptr;
+      break;
+    }
+    case Character_BookFan: {
+      auto ptr = reinterpret_cast<BookReader *>(value);
+      delete ptr;
+      break;
+    }
+    case Character_Other: {
+      auto ptr = reinterpret_cast<std::string *>(value);
+      delete ptr;
+      break;
+    }
+    case Character_Unused: {
+      auto ptr = reinterpret_cast<std::string *>(value);
+      delete ptr;
+      break;
+    }
+    default: break;
+  }
+  value = nullptr;
+  type = Character_NONE;
+}
+
 inline const Movie *GetMovie(const void *buf) {
   return flatbuffers::GetRoot<Movie>(buf);
 }
 
+inline Movie *GetMutableMovie(void *buf) {
+  return flatbuffers::GetMutableRoot<Movie>(buf);
+}
+
 inline const char *MovieIdentifier() {
   return "MOVI";
 }
@@ -297,4 +557,10 @@ inline void FinishMovieBuffer(
   fbb.Finish(root, MovieIdentifier());
 }
 
+inline std::unique_ptr<MovieT> UnPackMovie(
+    const void *buf,
+    const flatbuffers::resolver_function_t *res = nullptr) {
+  return std::unique_ptr<MovieT>(GetMovie(buf)->UnPack(res));
+}
+
 #endif  // FLATBUFFERS_GENERATED_UNIONVECTOR_H_