base/prefs/pref_store.h

   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
  14 namespace base {
  15 class 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.
  25 class 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_