1 // Copyright 2016 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef MOJO_PUBLIC_CPP_BINDINGS_UNION_TRAITS_H_ 6 #define MOJO_PUBLIC_CPP_BINDINGS_UNION_TRAITS_H_ 7 8 namespace mojo { 9 10 // This must be specialized for any type |T| to be serialized/deserialized as 11 // a mojom union. |DataViewType| is the corresponding data view type of the 12 // mojom union. For example, if the mojom union is example.Foo, |DataViewType| 13 // will be example::FooDataView, which can also be referred to by 14 // example::Foo::DataView (in chromium) and example::blink::Foo::DataView (in 15 // blink). 16 // 17 // Similar to StructTraits, each specialization of UnionTraits implements the 18 // following methods: 19 // 1. Getters for each field in the Mojom type. 20 // 2. Read() method. 21 // 3. [Optional] IsNull() and SetToNull(). 22 // 4. [Optional] SetUpContext() and TearDownContext(). 23 // Please see the documentation of StructTraits for details of these methods. 24 // 25 // Unlike StructTraits, there is one more method to implement: 26 // 5. A static GetTag() method indicating which field is the current active 27 // field for serialization: 28 // 29 // static DataViewType::Tag GetTag(const T& input); 30 // 31 // During serialization, only the field getter corresponding to this tag 32 // will be called. 33 // 34 template <typename DataViewType, typename T> 35 struct UnionTraits; 36 37 } // namespace mojo 38 39 #endif // MOJO_PUBLIC_CPP_BINDINGS_UNION_TRAITS_H_ 40
