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 // This defines helpful methods for dealing with Callbacks. Because Callbacks 6 // are implemented using templates, with a class per callback signature, adding 7 // methods to Callback<> itself is unattractive (lots of extra code gets 8 // generated). Instead, consider adding methods here. 9 // 10 // ResetAndReturn(&cb) is like cb.Reset() but allows executing a callback (via a 11 // move or copy) after the original callback is Reset(). This can be handy if 12 // Run() reads/writes the variable holding the Callback. 13 14 #ifndef BASE_CALLBACK_HELPERS_H_ 15 #define BASE_CALLBACK_HELPERS_H_ 16 17 #include "base/callback.h" 18 #include "base/compiler_specific.h" 19 #include "base/macros.h" 20 21 namespace base { 22 23 template <typename Signature, 24 internal::CopyMode copy_mode, 25 internal::RepeatMode repeat_mode> 26 base::Callback<Signature, copy_mode, repeat_mode> ResetAndReturn( 27 base::Callback<Signature, copy_mode, repeat_mode>* cb) { 28 base::Callback<Signature, copy_mode, repeat_mode> ret(std::move(*cb)); 29 DCHECK(!*cb); 30 return ret; 31 } 32 33 // ScopedClosureRunner is akin to std::unique_ptr<> for Closures. It ensures 34 // that the Closure is executed no matter how the current scope exits. 35 class BASE_EXPORT ScopedClosureRunner { 36 public: 37 ScopedClosureRunner(); 38 explicit ScopedClosureRunner(const Closure& closure); 39 ~ScopedClosureRunner(); 40 41 ScopedClosureRunner(ScopedClosureRunner&& other); 42 43 // Releases the current closure if it's set and replaces it with the closure 44 // from |other|. 45 ScopedClosureRunner& operator=(ScopedClosureRunner&& other); 46 47 // Calls the current closure and resets it, so it wont be called again. 48 void RunAndReset(); 49 50 // Replaces closure with the new one releasing the old one without calling it. 51 void ReplaceClosure(const Closure& closure); 52 53 // Releases the Closure without calling. 54 Closure Release() WARN_UNUSED_RESULT; 55 56 private: 57 Closure closure_; 58 59 DISALLOW_COPY_AND_ASSIGN(ScopedClosureRunner); 60 }; 61 62 } // namespace base 63 64 #endif // BASE_CALLBACK_HELPERS_H_ 65
