base/mac/bind_objc_block.h

   1 // Copyright (c) 2012 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 BASE_MAC_BIND_OBJC_BLOCK_H_
   6 #define BASE_MAC_BIND_OBJC_BLOCK_H_
   7
   8 #include <Block.h>
   9
  10 #include "base/bind.h"
  11 #include "base/callback_forward.h"
  12 #include "base/mac/scoped_block.h"
  13
  14 // BindBlock builds a callback from an Objective-C block. Example usages:
  15 //
  16 // Closure closure = BindBlock(^{DoSomething();});
  17 //
  18 // Callback<int(void)> callback = BindBlock(^{return 42;});
  19 //
  20 // Callback<void(const std::string&, const std::string&)> callback =
  21 //     BindBlock(^(const std::string& arg0, const std::string& arg1) {
  22 //         ...
  23 //     });
  24 //
  25 // These variadic templates will accommodate any number of arguments, however
  26 // the underlying templates in bind_internal.h and callback.h are limited to
  27 // seven total arguments, and the bound block itself is used as one of these
  28 // arguments, so functionally the templates are limited to binding blocks with
  29 // zero through six arguments.
  30
  31 namespace base {
  32
  33 namespace internal {
  34
  35 // Helper function to run the block contained in the parameter.
  36 template<typename R, typename... Args>
  37 R RunBlock(base::mac::ScopedBlock<R(^)(Args...)> block, Args... args) {
  38   R(^extracted_block)(Args...) = block.get();
  39   return extracted_block(args...);
  40 }
  41
  42 }  // namespace internal
  43
  44 // Construct a callback from an objective-C block with up to six arguments (see
  45 // note above).
  46 template<typename R, typename... Args>
  47 base::Callback<R(Args...)> BindBlock(R(^block)(Args...)) {
  48   return base::Bind(&base::internal::RunBlock<R, Args...>,
  49                     base::mac::ScopedBlock<R(^)(Args...)>(Block_copy(block)));
  50 }
  51
  52 }  // namespace base
  53
  54 #endif  // BASE_MAC_BIND_OBJC_BLOCK_H_