// Copyright (c) 2011 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. // Support for using the Singleton pattern with Objective-C objects. A // SingletonObjC is the same as a Singleton, except the default traits are // appropriate for Objective-C objects. A typical Objective-C object of type // NSExampleType can be maintained as a singleton and accessed with: // // NSExampleType* exampleSingleton = SingletonObjC::get(); // // The first time this is used, it will create exampleSingleton as the result // of [[NSExampleType alloc] init]. Subsequent calls will return the same // NSExampleType* object. The object will be released by calling // -[NSExampleType release] when Singleton's atexit routines run // (see singleton.h). // // For Objective-C objects initialized through means other than the // no-parameter -init selector, DefaultSingletonObjCTraits may be extended // as needed: // // struct FooSingletonTraits : public DefaultSingletonObjCTraits { // static Foo* New() { // return [[Foo alloc] initWithName:@"selecty"]; // } // }; // ... // Foo* widgetSingleton = SingletonObjC::get(); #ifndef BASE_MEMORY_SINGLETON_OBJC_H_ #define BASE_MEMORY_SINGLETON_OBJC_H_ #pragma once #import #include "base/memory/singleton.h" // Singleton traits usable to manage traditional Objective-C objects, which // are instantiated by sending |alloc| and |init| messages, and are deallocated // in a memory-managed environment when their retain counts drop to 0 by // sending |release| messages. template struct DefaultSingletonObjCTraits : public DefaultSingletonTraits { static Type* New() { return [[Type alloc] init]; } static void Delete(Type* object) { [object release]; } }; // Exactly like Singleton, but without the DefaultSingletonObjCTraits as the // default trait class. This makes it straightforward for Objective-C++ code // to hold Objective-C objects as singletons. template, typename DifferentiatingType = Type> class SingletonObjC : public Singleton { }; #endif // BASE_MEMORY_SINGLETON_OBJC_H_