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#include "base/logging.h"
13
14// ScopedObserver is used to keep track of the set of sources an object has
15// attached itself to as an observer. When ScopedObserver is destroyed it
16// removes the object as an observer from all sources it has been added to.
17template <class Source, class Observer>
18class ScopedObserver {
19 public:
20  explicit ScopedObserver(Observer* observer) : observer_(observer) {}
21
22  ~ScopedObserver() {
23    RemoveAll();
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    auto it = std::find(sources_.begin(), sources_.end(), source);
35    DCHECK(it != sources_.end());
36    sources_.erase(it);
37    source->RemoveObserver(observer_);
38  }
39
40  void RemoveAll() {
41    for (size_t i = 0; i < sources_.size(); ++i)
42      sources_[i]->RemoveObserver(observer_);
43    sources_.clear();
44  }
45
46  bool IsObserving(Source* source) const {
47    return std::find(sources_.begin(), sources_.end(), source) !=
48        sources_.end();
49  }
50
51 private:
52  Observer* observer_;
53
54  std::vector<Source*> sources_;
55
56  DISALLOW_COPY_AND_ASSIGN(ScopedObserver);
57};
58
59#endif  // BASE_SCOPED_OBSERVER_H_
60