base/prefs/pref_change_registrar.h

   1 // Copyright (c) 2010 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_CHANGE_REGISTRAR_H_
   6 #define BASE_PREFS_PREF_CHANGE_REGISTRAR_H_
   7
   8 #include <map>
   9 #include <string>
  10
  11 #include "base/basictypes.h"
  12 #include "base/callback.h"
  13 #include "base/prefs/base_prefs_export.h"
  14 #include "base/prefs/pref_observer.h"
  15
  16 class PrefService;
  17
  18 // Automatically manages the registration of one or more pref change observers
  19 // with a PrefStore. Functions much like NotificationRegistrar, but specifically
  20 // manages observers of preference changes. When the Registrar is destroyed,
  21 // all registered observers are automatically unregistered with the PrefStore.
  22 class BASE_PREFS_EXPORT PrefChangeRegistrar : public PrefObserver {
  23  public:
  24   // You can register this type of callback if you need to know the
  25   // path of the preference that is changing.
  26   typedef base::Callback<void(const std::string&)> NamedChangeCallback;
  27
  28   PrefChangeRegistrar();
  29   virtual ~PrefChangeRegistrar();
  30
  31   // Must be called before adding or removing observers. Can be called more
  32   // than once as long as the value of |service| doesn't change.
  33   void Init(PrefService* service);
  34
  35   // Adds a pref observer for the specified pref |path| and |obs| observer
  36   // object. All registered observers will be automatically unregistered
  37   // when the registrar's destructor is called.
  38   //
  39   // The second version binds a callback that will receive the path of
  40   // the preference that is changing as its parameter.
  41   //
  42   // Only one observer may be registered per path.
  43   void Add(const std::string& path, const base::Closure& obs);
  44   void Add(const std::string& path, const NamedChangeCallback& obs);
  45
  46   // Removes the pref observer registered for |path|.
  47   void Remove(const std::string& path);
  48
  49   // Removes all observers that have been previously added with a call to Add.
  50   void RemoveAll();
  51
  52   // Returns true if no pref observers are registered.
  53   bool IsEmpty() const;
  54
  55   // Check whether |pref| is in the set of preferences being observed.
  56   bool IsObserved(const std::string& pref);
  57
  58   // Check whether any of the observed preferences has the managed bit set.
  59   bool IsManaged();
  60
  61   // Return the PrefService for this registrar.
  62   PrefService* prefs();
  63   const PrefService* prefs() const;
  64
  65  private:
  66   // PrefObserver:
  67   void OnPreferenceChanged(PrefService* service,
  68                            const std::string& pref_name) override;
  69
  70   static void InvokeUnnamedCallback(const base::Closure& callback,
  71                                     const std::string& pref_name);
  72
  73   typedef std::map<std::string, NamedChangeCallback> ObserverMap;
  74
  75   ObserverMap observers_;
  76   PrefService* service_;
  77
  78   DISALLOW_COPY_AND_ASSIGN(PrefChangeRegistrar);
  79 };
  80
  81 #endif  // BASE_PREFS_PREF_CHANGE_REGISTRAR_H_