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// Copyright (c) 2010 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 BASE_PREFS_PREF_CHANGE_REGISTRAR_H_
#define BASE_PREFS_PREF_CHANGE_REGISTRAR_H_
#include <map>
#include <string>
#include "base/basictypes.h"
#include "base/callback.h"
#include "base/prefs/base_prefs_export.h"
#include "base/prefs/pref_observer.h"
class PrefService;
// Automatically manages the registration of one or more pref change observers
// with a PrefStore. Functions much like NotificationRegistrar, but specifically
// manages observers of preference changes. When the Registrar is destroyed,
// all registered observers are automatically unregistered with the PrefStore.
class BASE_PREFS_EXPORT PrefChangeRegistrar : public PrefObserver {
public:
// You can register this type of callback if you need to know the
// path of the preference that is changing.
typedef base::Callback<void(const std::string&)> NamedChangeCallback;
PrefChangeRegistrar();
virtual ~PrefChangeRegistrar();
// Must be called before adding or removing observers. Can be called more
// than once as long as the value of |service| doesn't change.
void Init(PrefService* service);
// Adds a pref observer for the specified pref |path| and |obs| observer
// object. All registered observers will be automatically unregistered
// when the registrar's destructor is called.
//
// The second version binds a callback that will receive the path of
// the preference that is changing as its parameter.
//
// Only one observer may be registered per path.
void Add(const char* path, const base::Closure& obs);
void Add(const char* path, const NamedChangeCallback& obs);
// Removes the pref observer registered for |path|.
void Remove(const char* path);
// Removes all observers that have been previously added with a call to Add.
void RemoveAll();
// Returns true if no pref observers are registered.
bool IsEmpty() const;
// Check whether |pref| is in the set of preferences being observed.
bool IsObserved(const std::string& pref);
// Check whether any of the observed preferences has the managed bit set.
bool IsManaged();
// Return the PrefService for this registrar.
PrefService* prefs();
const PrefService* prefs() const;
private:
// PrefObserver:
virtual void OnPreferenceChanged(PrefService* service,
const std::string& pref_name) OVERRIDE;
static void InvokeUnnamedCallback(const base::Closure& callback,
const std::string& pref_name);
typedef std::map<std::string, NamedChangeCallback> ObserverMap;
ObserverMap observers_;
PrefService* service_;
DISALLOW_COPY_AND_ASSIGN(PrefChangeRegistrar);
};
#endif // BASE_PREFS_PREF_CHANGE_REGISTRAR_H_
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