base/callback_helpers.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 // 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/basictypes.h"
  18 #include "base/callback.h"
  19 #include "base/compiler_specific.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 scoped_ptr for Closures. It ensures that the
  31 // Closure is executed and deleted 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   void Reset();
  39   void Reset(const Closure& closure);
  40   Closure Release() WARN_UNUSED_RESULT;
  41
  42  private:
  43   Closure closure_;
  44
  45   DISALLOW_COPY_AND_ASSIGN(ScopedClosureRunner);
  46 };
  47
  48 }  // namespace base
  49
  50 #endif  // BASE_CALLBACK_HELPERS_H_