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 #include "base/stl_util.h" 16 17 // ScopedObserver is used to keep track of the set of sources an object has 18 // attached itself to as an observer. When ScopedObserver is destroyed it 19 // removes the object as an observer from all sources it has been added to. 20 template <class Source, class Observer> 21 class ScopedObserver { 22 public: 23 explicit ScopedObserver(Observer* observer) : observer_(observer) {} 24 25 ~ScopedObserver() { 26 RemoveAll(); 27 } 28 29 // Adds the object passed to the constructor as an observer on |source|. 30 void Add(Source* source) { 31 sources_.push_back(source); 32 source->AddObserver(observer_); 33 } 34 35 // Remove the object passed to the constructor as an observer from |source|. 36 void Remove(Source* source) { 37 auto it = std::find(sources_.begin(), sources_.end(), source); 38 DCHECK(it != sources_.end()); 39 sources_.erase(it); 40 source->RemoveObserver(observer_); 41 } 42 43 void RemoveAll() { 44 for (size_t i = 0; i < sources_.size(); ++i) 45 sources_[i]->RemoveObserver(observer_); 46 sources_.clear(); 47 } 48 49 bool IsObserving(Source* source) const { 50 return base::ContainsValue(sources_, source); 51 } 52 53 bool IsObservingSources() const { return !sources_.empty(); } 54 55 private: 56 Observer* observer_; 57 58 std::vector<Source*> sources_; 59 60 DISALLOW_COPY_AND_ASSIGN(ScopedObserver); 61 }; 62 63 #endif // BASE_SCOPED_OBSERVER_H_ 64
