mmentovai@google.com | 3d02802 | 2008-08-29 02:40:59 +0900 | [diff] [blame] | 1 | // Copyright (c) 2008 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 | // Support for using the Singleton<T> pattern with Objective-C objects. A |
| 6 | // SingletonObjC is the same as a Singleton, except the default traits are |
| 7 | // appropriate for Objective-C objects. A typical Objective-C object of type |
| 8 | // NSExampleType can be maintained as a singleton and accessed with: |
| 9 | // |
| 10 | // NSExampleType* exampleSingleton = SingletonObjC<NSExampleType>::get(); |
| 11 | // |
| 12 | // The first time this is used, it will create exampleSingleton as the result |
| 13 | // of [[NSExampleType alloc] init]. Subsequent calls will return the same |
| 14 | // NSExampleType* object. The object will be released by calling |
| 15 | // -[NSExampleType release] when Singleton's atexit routines run |
| 16 | // (see singleton.h). |
| 17 | // |
| 18 | // For Objective-C objects initialized through means other than the |
| 19 | // no-parameter -init selector, DefaultSingletonObjCTraits may be extended |
| 20 | // as needed: |
| 21 | // |
| 22 | // struct FooSingletonTraits : public DefaultSingletonObjCTraits<Foo> { |
| 23 | // static Foo* New() { |
| 24 | // return [[Foo alloc] initWithName:@"selecty"]; |
| 25 | // } |
| 26 | // } |
| 27 | // ... |
| 28 | // Foo* widgetSingleton = SingletonObjC<Foo, FooSingletonTraits>::get(); |
| 29 | |
| 30 | #ifndef BASE_SINGLETON_OBJC_H_ |
| 31 | #define BASE_SINGLETON_OBJC_H_ |
| 32 | |
| 33 | #import <Foundation/Foundation.h> |
| 34 | #include "base/singleton.h" |
| 35 | |
| 36 | // Singleton traits usable to manage traditional Objective-C objects, which |
| 37 | // are instantiated by sending |alloc| and |init| messages, and are deallocated |
| 38 | // in a memory-managed environment when their retain counts drop to 0 by |
| 39 | // sending |release| messages. |
| 40 | template<typename Type> |
| 41 | struct DefaultSingletonObjCTraits : public DefaultSingletonTraits<Type> { |
| 42 | static Type* New() { |
| 43 | return [[Type alloc] init]; |
| 44 | } |
| 45 | |
| 46 | static void Delete(Type* object) { |
| 47 | [object release]; |
| 48 | } |
| 49 | }; |
| 50 | |
| 51 | // Exactly like Singleton, but without the DefaultSingletonObjCTraits as the |
| 52 | // default trait class. This makes it straightforward for Objective-C++ code |
| 53 | // to hold Objective-C objects as singletons. |
| 54 | template<typename Type, |
| 55 | typename Traits = DefaultSingletonObjCTraits<Type>, |
| 56 | typename DifferentiatingType = Type> |
| 57 | class SingletonObjC : public Singleton<Type, Traits, DifferentiatingType> { |
| 58 | }; |
| 59 | |
| 60 | #endif // BASE_SINGLETON_OBJC_H_ |