1 files changed, 53 insertions, 0 deletions
diff --git a/ash/wm/scoped_observer.h b/ash/wm/scoped_observer.h
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+++ b/ash/wm/scoped_observer.h
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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_WM_SCOPED_OBSERVER_H_
+#define ASH_WM_SCOPED_OBSERVER_H_
+#pragma once
+
+#include <algorithm>
+#include <vector>
+
+#include "base/basictypes.h"
+
+namespace ash {
+namespace internal {
+
+// ScopedObserver is used to keep track of the set of sources an object has
+// attached itself to as an observer. When ScopedObserver is destroyed it
+// removes the object as an observer from all sources it has been added to.
+template <class Source, class Observer>
+class ScopedObserver {
+ public:
+  explicit ScopedObserver(Observer* observer) : observer_(observer) {}
+
+  ~ScopedObserver() {
+    for (size_t i = 0; i < sources_.size(); ++i)
+      sources_[i]->RemoveObserver(observer_);
+  }
+
+  // Adds the object passed to the constructor as an observer on |source|.
+  void Add(Source* source) {
+    sources_.push_back(source);
+    source->AddObserver(observer_);
+  }
+
+  // Removse the object passed to the constructor as an observer from |source|.
+  void Remove(Source* source) {
+    sources_.erase(std::find(sources_.begin(), sources_.end(), source));
+    source->RemoveObserver(observer_);
+  }
+
+ private:
+  Observer* observer_;
+
+  std::vector<Source*> sources_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedObserver);
+};
+
+}  // namespace internal
+}  // namespace ash
+
+#endif  // ASH_WM_SCOPED_OBSERVER_H_