pref_store.h revision 424c4d7b64af9d0d8fd9624f381f469654d5e3d2 
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_PREFS_PREF_STORE_H_
6#define BASE_PREFS_PREF_STORE_H_
7
8#include <string>
9
10#include "base/basictypes.h"
11#include "base/memory/ref_counted.h"
12#include "base/prefs/base_prefs_export.h"
13
14namespace base {
15class Value;
16}
17
18// This is an abstract interface for reading and writing from/to a persistent
19// preference store, used by PrefService. An implementation using a JSON file
20// can be found in JsonPrefStore, while an implementation without any backing
21// store for testing can be found in TestingPrefStore. Furthermore, there is
22// CommandLinePrefStore, which bridges command line options to preferences and
23// ConfigurationPolicyPrefStore, which is used for hooking up configuration
24// policy with the preference subsystem.
25class BASE_PREFS_EXPORT PrefStore : public base::RefCounted<PrefStore> {
26 public:
27  // Observer interface for monitoring PrefStore.
28  class BASE_PREFS_EXPORT Observer {
29   public:
30    // Called when the value for the given |key| in the store changes.
31    virtual void OnPrefValueChanged(const std::string& key) = 0;
32    // Notification about the PrefStore being fully initialized.
33    virtual void OnInitializationCompleted(bool succeeded) = 0;
34
35   protected:
36    virtual ~Observer() {}
37  };
38
39  PrefStore() {}
40
41  // Add and remove observers.
42  virtual void AddObserver(Observer* observer) {}
43  virtual void RemoveObserver(Observer* observer) {}
44  virtual bool HasObservers() const;
45
46  // Whether the store has completed all asynchronous initialization.
47  virtual bool IsInitializationComplete() const;
48
49  // Get the value for a given preference |key| and stores it in |*result|.
50  // |*result| is only modified if the return value is true and if |result|
51  // is not NULL. Ownership of the |*result| value remains with the PrefStore.
52  virtual bool GetValue(const std::string& key,
53                        const base::Value** result) const = 0;
54
55 protected:
56  friend class base::RefCounted<PrefStore>;
57  virtual ~PrefStore() {}
58
59 private:
60  DISALLOW_COPY_AND_ASSIGN(PrefStore);
61};
62
63#endif  // BASE_PREFS_PREF_STORE_H_
64