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.
16template <class Source, class Observer>
17class 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_
55