Home | History | Annotate | Download | only in base 
      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>
     24 base::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