1 // Copyright 2014 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_TYPE_CONVERTER_H_ 6 #define MOJO_PUBLIC_CPP_BINDINGS_TYPE_CONVERTER_H_ 7 8 namespace mojo { 9 10 // Specialize the following class: 11 // template <typename T, typename U> class TypeConverter; 12 // to perform type conversion for Mojom-defined structs and arrays. Here, T is 13 // the Mojom-defined struct or array, and U is some other non-Mojom 14 // struct or array type. 15 // 16 // Specializations should implement the following interface: 17 // namespace mojo { 18 // template <> 19 // class TypeConverter<T, U> { 20 // public: 21 // static T ConvertFrom(const U& input); 22 // static U ConvertTo(const T& input); 23 // }; 24 // } 25 // 26 // EXAMPLE: 27 // 28 // Suppose you have the following Mojom-defined struct: 29 // 30 // module geometry { 31 // struct Point { 32 // int32 x; 33 // int32 y; 34 // }; 35 // } 36 // 37 // Now, imagine you wanted to write a TypeConverter specialization for 38 // gfx::Point. It might look like this: 39 // 40 // namespace mojo { 41 // template <> 42 // class TypeConverter<geometry::PointPtr, gfx::Point> { 43 // public: 44 // static geometry::PointPtr ConvertFrom(const gfx::Point& input) { 45 // geometry::PointPtr result; 46 // result->x = input.x(); 47 // result->y = input.y(); 48 // return result.Pass(); 49 // } 50 // static gfx::Point ConvertTo(const geometry::PointPtr& input) { 51 // return input ? gfx::Point(input->x, input->y) : gfx::Point(); 52 // } 53 // }; 54 // } 55 // 56 // With the above TypeConverter defined, it is possible to write code like this: 57 // 58 // void AcceptPoint(const geometry::PointPtr& input) { 59 // // With an explicit cast using the .To<> method. 60 // gfx::Point pt = input.To<gfx::Point>(); 61 // 62 // // With an explicit cast using the static From() method. 63 // geometry::PointPtr output = geometry::Point::From(pt); 64 // } 65 // 66 template <typename T, typename U> class TypeConverter; 67 68 // The following specialization is useful when you are converting between 69 // Array<POD> and std::vector<POD>. 70 template <typename T> class TypeConverter<T, T> { 71 public: ConvertFrom(const T & obj)72 static T ConvertFrom(const T& obj) { 73 return obj; 74 } ConvertTo(const T & obj)75 static T ConvertTo(const T& obj) { 76 return obj; 77 } 78 }; 79 80 } // namespace mojo 81 82 #endif // MOJO_PUBLIC_CPP_BINDINGS_TYPE_CONVERTER_H_ 83