1 // Copyright 2010 The Chromium Authors 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 COMPONENTS_PREFS_PREF_CHANGE_REGISTRAR_H_ 6 #define COMPONENTS_PREFS_PREF_CHANGE_REGISTRAR_H_ 7 8 #include <map> 9 #include <string> 10 11 #include "base/functional/callback.h" 12 #include "base/memory/raw_ptr.h" 13 #include "components/prefs/pref_observer.h" 14 #include "components/prefs/prefs_export.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 COMPONENTS_PREFS_EXPORT PrefChangeRegistrar final : 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 using NamedChangeCallback = base::RepeatingCallback<void(const std::string&)>; 27 28 PrefChangeRegistrar(); 29 30 PrefChangeRegistrar(const PrefChangeRegistrar&) = delete; 31 PrefChangeRegistrar& operator=(const PrefChangeRegistrar&) = delete; 32 33 ~PrefChangeRegistrar(); 34 35 // Must be called before adding or removing observers. Can be called more 36 // than once as long as the value of |service| doesn't change. 37 void Init(PrefService* service); 38 39 // Adds a pref observer for the specified pref |path| and |obs| observer 40 // object. All registered observers will be automatically unregistered 41 // when the registrar's destructor is called. 42 // 43 // The second version binds a callback that will receive the path of 44 // the preference that is changing as its parameter. 45 // 46 // Only one observer may be registered per path. 47 void Add(const std::string& path, const base::RepeatingClosure& obs); 48 void Add(const std::string& path, const NamedChangeCallback& obs); 49 50 // Removes the pref observer registered for |path|. 51 void Remove(const std::string& path); 52 53 // Removes all observers that have been previously added with a call to Add. 54 void RemoveAll(); 55 56 // Returns true if no pref observers are registered. 57 bool IsEmpty() const; 58 59 // Check whether |pref| is in the set of preferences being observed. 60 bool IsObserved(const std::string& pref); 61 62 // Return the PrefService for this registrar. 63 PrefService* prefs(); 64 const PrefService* prefs() const; 65 66 private: 67 // PrefObserver: 68 void OnPreferenceChanged(PrefService* service, 69 const std::string& pref_name) override; 70 71 static void InvokeUnnamedCallback(const base::RepeatingClosure& callback, 72 const std::string& pref_name); 73 74 using ObserverMap = std::map<std::string, NamedChangeCallback>; 75 76 ObserverMap observers_; 77 raw_ptr<PrefService, DanglingUntriaged> service_; 78 }; 79 80 #endif // COMPONENTS_PREFS_PREF_CHANGE_REGISTRAR_H_ 81