render_frame_observer_tracker.h revision a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7 
1// Copyright 2013 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// Helper class used to find the RenderFrameObservers for a given RenderFrame.
6//
7// Example usage:
8//
9//   class MyRFO : public RenderFrameObserver,
10//                 public RenderFrameObserverTracker<MyRFO> {
11//     ...
12//   };
13//
14//   MyRFO::MyRFO(RenderFrame* render_frame)
15//       : RenderFrameObserver(render_frame),
16//         RenderFrameObserverTracker<MyRFO>(render_frame) {
17//     ...
18//   }
19//
20//  void SomeFunction(RenderFrame* rf) {
21//    MyRFO* my_rfo = new MyRFO(rf);
22//    MyRFO* my_rfo_tracked = MyRFO::Get(rf);
23//    // my_rfo == my_rfo_tracked
24//  }
25
26#ifndef CONTENT_PUBLIC_RENDERER_RENDER_FRAME_OBSERVER_TRACKER_H_
27#define CONTENT_PUBLIC_RENDERER_RENDER_FRAME_OBSERVER_TRACKER_H_
28
29#include <map>
30
31#include "base/lazy_instance.h"
32
33namespace content {
34
35class RenderFrame;
36
37template <class T>
38class RenderFrameObserverTracker {
39 public:
40  static T* Get(const RenderFrame* render_frame) {
41    return render_frame_map_.Get()[render_frame];
42  }
43
44  explicit RenderFrameObserverTracker(const RenderFrame* render_frame)
45      : render_frame_(render_frame) {
46    render_frame_map_.Get()[render_frame] = static_cast<T*>(this);
47  }
48  ~RenderFrameObserverTracker() {
49    render_frame_map_.Get().erase(render_frame_);
50  }
51
52 private:
53  const RenderFrame* render_frame_;
54
55  static base::LazyInstance<std::map<const RenderFrame*, T*> >
56    render_frame_map_;
57
58  DISALLOW_COPY_AND_ASSIGN(RenderFrameObserverTracker<T>);
59};
60
61template <class T>
62base::LazyInstance<std::map<const RenderFrame*, T*> >
63    RenderFrameObserverTracker<T>::render_frame_map_ =
64        LAZY_INSTANCE_INITIALIZER;
65
66}  // namespace content
67
68#endif  // CONTENT_PUBLIC_RENDERER_RENDER_FRAME_OBSERVER_TRACKER_H_
69