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// Copyright 2010 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_PREFS_PREF_CHANGE_REGISTRAR_H_
#define COMPONENTS_PREFS_PREF_CHANGE_REGISTRAR_H_
#include <map>
#include <string>
#include "base/functional/callback.h"
#include "base/memory/raw_ptr.h"
#include "components/prefs/pref_observer.h"
#include "components/prefs/prefs_export.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 COMPONENTS_PREFS_EXPORT PrefChangeRegistrar final : public PrefObserver {
public:
// You can register this type of callback if you need to know the
// path of the preference that is changing.
using NamedChangeCallback = base::RepeatingCallback<void(const std::string&)>;
PrefChangeRegistrar();
PrefChangeRegistrar(const PrefChangeRegistrar&) = delete;
PrefChangeRegistrar& operator=(const PrefChangeRegistrar&) = delete;
~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 std::string& path, const base::RepeatingClosure& obs);
void Add(const std::string& path, const NamedChangeCallback& obs);
// Removes the pref observer registered for |path|.
void Remove(const std::string& 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);
// Return the PrefService for this registrar.
PrefService* prefs();
const PrefService* prefs() const;
private:
// PrefObserver:
void OnPreferenceChanged(PrefService* service,
const std::string& pref_name) override;
static void InvokeUnnamedCallback(const base::RepeatingClosure& callback,
const std::string& pref_name);
using ObserverMap = std::map<std::string, NamedChangeCallback>;
ObserverMap observers_;
raw_ptr<PrefService, AcrossTasksDanglingUntriaged> service_;
};
#endif // COMPONENTS_PREFS_PREF_CHANGE_REGISTRAR_H_
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