OLD | NEW |
1 // Copyright 2013 The Chromium Authors. All rights reserved. | 1 // Copyright 2013 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
| 4 // |
| 5 // A helper class that assists preferences in firing notifications when lists |
| 6 // or dictionaries are changed. |
4 | 7 |
5 // TODO(brettw) remove this forwarding header when prefs is completely moved to | 8 #ifndef BASE_PREFS_SCOPED_USER_PREF_UPDATE_H_ |
6 // components. | 9 #define BASE_PREFS_SCOPED_USER_PREF_UPDATE_H_ |
7 #include "components/prefs/scoped_user_pref_update.h" | 10 |
| 11 #include <string> |
| 12 |
| 13 #include "base/macros.h" |
| 14 #include "base/prefs/base_prefs_export.h" |
| 15 #include "base/prefs/pref_service.h" |
| 16 #include "base/threading/non_thread_safe.h" |
| 17 #include "base/values.h" |
| 18 |
| 19 class PrefService; |
| 20 |
| 21 namespace base { |
| 22 class DictionaryValue; |
| 23 class ListValue; |
| 24 } |
| 25 |
| 26 namespace subtle { |
| 27 |
| 28 // Base class for ScopedUserPrefUpdateTemplate that contains the parts |
| 29 // that do not depend on ScopedUserPrefUpdateTemplate's template parameter. |
| 30 // |
| 31 // We need this base class mostly for making it a friend of PrefService |
| 32 // and getting access to PrefService::GetMutableUserPref and |
| 33 // PrefService::ReportUserPrefChanged. |
| 34 class BASE_PREFS_EXPORT ScopedUserPrefUpdateBase : public base::NonThreadSafe { |
| 35 protected: |
| 36 ScopedUserPrefUpdateBase(PrefService* service, const std::string& path); |
| 37 |
| 38 // Calls Notify(). |
| 39 ~ScopedUserPrefUpdateBase(); |
| 40 |
| 41 // Sets |value_| to |service_|->GetMutableUserPref and returns it. |
| 42 base::Value* GetValueOfType(base::Value::Type type); |
| 43 |
| 44 private: |
| 45 // If |value_| is not null, triggers a notification of PrefObservers and |
| 46 // resets |value_|. |
| 47 void Notify(); |
| 48 |
| 49 // Weak pointer. |
| 50 PrefService* service_; |
| 51 // Path of the preference being updated. |
| 52 std::string path_; |
| 53 // Cache of value from user pref store (set between Get() and Notify() calls). |
| 54 base::Value* value_; |
| 55 |
| 56 DISALLOW_COPY_AND_ASSIGN(ScopedUserPrefUpdateBase); |
| 57 }; |
| 58 |
| 59 } // namespace subtle |
| 60 |
| 61 // Class to support modifications to DictionaryValues and ListValues while |
| 62 // guaranteeing that PrefObservers are notified of changed values. |
| 63 // |
| 64 // This class may only be used on the UI thread as it requires access to the |
| 65 // PrefService. |
| 66 template <typename T, base::Value::Type type_enum_value> |
| 67 class ScopedUserPrefUpdate : public subtle::ScopedUserPrefUpdateBase { |
| 68 public: |
| 69 ScopedUserPrefUpdate(PrefService* service, const std::string& path) |
| 70 : ScopedUserPrefUpdateBase(service, path) {} |
| 71 |
| 72 // Triggers an update notification if Get() was called. |
| 73 virtual ~ScopedUserPrefUpdate() {} |
| 74 |
| 75 // Returns a mutable |T| instance that |
| 76 // - is already in the user pref store, or |
| 77 // - is (silently) created and written to the user pref store if none existed |
| 78 // before. |
| 79 // |
| 80 // Calling Get() implies that an update notification is necessary at |
| 81 // destruction time. |
| 82 // |
| 83 // The ownership of the return value remains with the user pref store. |
| 84 // Virtual so it can be overriden in subclasses that transform the value |
| 85 // before returning it (for example to return a subelement of a dictionary). |
| 86 virtual T* Get() { |
| 87 return static_cast<T*>(GetValueOfType(type_enum_value)); |
| 88 } |
| 89 |
| 90 T& operator*() { |
| 91 return *Get(); |
| 92 } |
| 93 |
| 94 T* operator->() { |
| 95 return Get(); |
| 96 } |
| 97 |
| 98 private: |
| 99 DISALLOW_COPY_AND_ASSIGN(ScopedUserPrefUpdate); |
| 100 }; |
| 101 |
| 102 typedef ScopedUserPrefUpdate<base::DictionaryValue, |
| 103 base::Value::TYPE_DICTIONARY> |
| 104 DictionaryPrefUpdate; |
| 105 typedef ScopedUserPrefUpdate<base::ListValue, base::Value::TYPE_LIST> |
| 106 ListPrefUpdate; |
| 107 |
| 108 #endif // BASE_PREFS_SCOPED_USER_PREF_UPDATE_H_ |
OLD | NEW |