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: ScopedObserver(Observer * observer)19 explicit ScopedObserver(Observer* observer) : observer_(observer) {} 20 ~ScopedObserver()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|. Add(Source * 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|. Remove(Source * source)33 void Remove(Source* source) { 34 sources_.erase(std::find(sources_.begin(), sources_.end(), source)); 35 source->RemoveObserver(observer_); 36 } 37 IsObserving(Source * source)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_ 55