base/prefs/pref_registry.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_REGISTRY_H_
   6 #define BASE_PREFS_PREF_REGISTRY_H_
   7
   8 #include "base/callback.h"
   9 #include "base/memory/ref_counted.h"
  10 #include "base/prefs/base_prefs_export.h"
  11 #include "base/prefs/pref_value_map.h"
  12
  13 namespace base {
  14 class Value;
  15 }
  16
  17 class DefaultPrefStore;
  18 class PrefStore;
  19
  20 // Preferences need to be registered with a type and default value
  21 // before they are used.
  22 //
  23 // The way you use a PrefRegistry is that you register all required
  24 // preferences on it (via one of its subclasses), then pass it as a
  25 // construction parameter to PrefService.
  26 //
  27 // Currently, registrations after constructing the PrefService will
  28 // also work, but this is being deprecated.
  29 class BASE_PREFS_EXPORT PrefRegistry : public base::RefCounted<PrefRegistry> {
  30  public:
  31   typedef PrefValueMap::const_iterator const_iterator;
  32   typedef base::Callback<void(const char*, base::Value*)> RegistrationCallback;
  33
  34   PrefRegistry();
  35
  36   // Gets the registered defaults.
  37   scoped_refptr<PrefStore> defaults();
  38
  39   // Allows iteration over defaults.
  40   const_iterator begin() const;
  41   const_iterator end() const;
  42
  43   // Changes the default value for a preference. Takes ownership of |value|.
  44   //
  45   // |pref_name| must be a previously registered preference.
  46   void SetDefaultPrefValue(const char* pref_name, base::Value* value);
  47
  48   // Exactly one callback can be set for registration. The callback
  49   // will be invoked each time registration has been performed on this
  50   // object.
  51   //
  52   // Calling this method after a callback has already been set will
  53   // make the object forget the previous callback and use the new one
  54   // instead.
  55   void SetRegistrationCallback(const RegistrationCallback& callback);
  56
  57  protected:
  58   friend class base::RefCounted<PrefRegistry>;
  59   virtual ~PrefRegistry();
  60
  61   // Used by subclasses to register a default value for a preference.
  62   void RegisterPreference(const char* path, base::Value* default_value);
  63
  64   scoped_refptr<DefaultPrefStore> defaults_;
  65
  66  private:
  67   RegistrationCallback registration_callback_;
  68
  69   DISALLOW_COPY_AND_ASSIGN(PrefRegistry);
  70 };
  71
  72 #endif  // BASE_PREFS_PREF_REGISTRY_H_