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.
20template <class Source, class Observer>
21class 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 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