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 // copy) after the original callback is Reset(). This can be handy if Run() 12 // 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 Sig> ResetAndReturn(base::Callback<Sig> * cb)24base::Callback<Sig> ResetAndReturn(base::Callback<Sig>* cb) { 25 base::Callback<Sig> ret(*cb); 26 cb->Reset(); 27 return ret; 28 } 29 30 // ScopedClosureRunner is akin to std::unique_ptr<> for Closures. It ensures 31 // that the Closure is executed no matter how the current scope exits. 32 class BASE_EXPORT ScopedClosureRunner { 33 public: 34 ScopedClosureRunner(); 35 explicit ScopedClosureRunner(const Closure& closure); 36 ~ScopedClosureRunner(); 37 38 ScopedClosureRunner(ScopedClosureRunner&& other); 39 40 // Releases the current closure if it's set and replaces it with the closure 41 // from |other|. 42 ScopedClosureRunner& operator=(ScopedClosureRunner&& other); 43 44 // Calls the current closure and resets it, so it wont be called again. 45 void RunAndReset(); 46 47 // Replaces closure with the new one releasing the old one without calling it. 48 void ReplaceClosure(const Closure& closure); 49 50 // Releases the Closure without calling. 51 Closure Release() WARN_UNUSED_RESULT; 52 53 private: 54 Closure closure_; 55 56 DISALLOW_COPY_AND_ASSIGN(ScopedClosureRunner); 57 }; 58 59 } // namespace base 60 61 #endif // BASE_CALLBACK_HELPERS_H_ 62