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 <stddef.h> 9 10 #include <algorithm> 11 #include <vector> 12 13 #include "base/logging.h" 14 #include "base/macros.h" 15 16 // ScopedObserver is used to keep track of the set of sources an object has 17 // attached itself to as an observer. When ScopedObserver is destroyed it 18 // removes the object as an observer from all sources it has been added to. 19 template <class Source, class Observer> 20 class ScopedObserver { 21 public: 22 explicit ScopedObserver(Observer* observer) : observer_(observer) {} 23 24 ~ScopedObserver() { 25 RemoveAll(); 26 } 27 28 // Adds the object passed to the constructor as an observer on |source|. 29 void Add(Source* source) { 30 sources_.push_back(source); 31 source->AddObserver(observer_); 32 } 33 34 // Remove the object passed to the constructor as an observer from |source|. 35 void Remove(Source* source) { 36 auto it = std::find(sources_.begin(), sources_.end(), source); 37 DCHECK(it != sources_.end()); 38 sources_.erase(it); 39 source->RemoveObserver(observer_); 40 } 41 42 void RemoveAll() { 43 for (size_t i = 0; i < sources_.size(); ++i) 44 sources_[i]->RemoveObserver(observer_); 45 sources_.clear(); 46 } 47 48 bool IsObserving(Source* source) const { 49 return ContainsValue(sources_, source); 50 } 51 52 bool IsObservingSources() const { return !sources_.empty(); } 53 54 private: 55 Observer* observer_; 56 57 std::vector<Source*> sources_; 58 59 DISALLOW_COPY_AND_ASSIGN(ScopedObserver); 60 }; 61 62 #endif // BASE_SCOPED_OBSERVER_H_ 63
