base/scoped_observer.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_SCOPED_OBSERVER_H_
   6 #define BASE_SCOPED_OBSERVER_H_
   7
   8 #include <algorithm>
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12
  13 // ScopedObserver is used to keep track of the set of sources an object has
  14 // attached itself to as an observer. When ScopedObserver is destroyed it
  15 // removes the object as an observer from all sources it has been added to.
  16 template <class Source, class Observer>
  17 class ScopedObserver {
  18  public:
  19   explicit ScopedObserver(Observer* observer) : observer_(observer) {}
  20
  21   ~ScopedObserver() {
  22     for (size_t i = 0; i < sources_.size(); ++i)
  23       sources_[i]->RemoveObserver(observer_);
  24   }
  25
  26   // Adds the object passed to the constructor as an observer on |source|.
  27   void Add(Source* source) {
  28     sources_.push_back(source);
  29     source->AddObserver(observer_);
  30   }
  31
  32   // Remove the object passed to the constructor as an observer from |source|.
  33   void Remove(Source* source) {
  34     sources_.erase(std::find(sources_.begin(), sources_.end(), source));
  35     source->RemoveObserver(observer_);
  36   }
  37
  38   bool IsObserving(Source* source) const {
  39     for (size_t i = 0; i < sources_.size(); ++i) {
  40       if (sources_[i] == source)
  41         return true;
  42     }
  43     return false;
  44   }
  45
  46  private:
  47   Observer* observer_;
  48
  49   std::vector<Source*> sources_;
  50
  51   DISALLOW_COPY_AND_ASSIGN(ScopedObserver);
  52 };
  53
  54 #endif  // BASE_SCOPED_OBSERVER_H_