| // Copyright 2016 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef MOJO_PUBLIC_CPP_BINDINGS_UNION_TRAITS_H_ |
| #define MOJO_PUBLIC_CPP_BINDINGS_UNION_TRAITS_H_ |
| |
| namespace mojo { |
| |
| // This must be specialized for any type |T| to be serialized/deserialized as |
| // a mojom union. |DataViewType| is the corresponding data view type of the |
| // mojom union. For example, if the mojom union is example.Foo, |DataViewType| |
| // will be example::FooDataView, which can also be referred to by |
| // example::Foo::DataView (in chromium) and example::blink::Foo::DataView (in |
| // blink). |
| // |
| // Similar to StructTraits, each specialization of UnionTraits implements the |
| // following methods: |
| // 1. Getters for each field in the Mojom type. |
| // 2. Read() method. |
| // 3. [Optional] IsNull() and SetToNull(). |
| // 4. [Optional] SetUpContext() and TearDownContext(). |
| // Please see the documentation of StructTraits for details of these methods. |
| // |
| // Unlike StructTraits, there is one more method to implement: |
| // 5. A static GetTag() method indicating which field is the current active |
| // field for serialization: |
| // |
| // static DataViewType::Tag GetTag(const T& input); |
| // |
| // During serialization, only the field getter corresponding to this tag |
| // will be called. |
| // |
| template <typename DataViewType, typename T> |
| struct UnionTraits; |
| |
| } // namespace mojo |
| |
| #endif // MOJO_PUBLIC_CPP_BINDINGS_UNION_TRAITS_H_ |
