1// Copyright (c) 2011 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_MEMORY_SINGLETON_OBJC_H_ 31#define BASE_MEMORY_SINGLETON_OBJC_H_ 32#pragma once 33 34#import <Foundation/Foundation.h> 35#include "base/memory/singleton.h" 36 37// Singleton traits usable to manage traditional Objective-C objects, which 38// are instantiated by sending |alloc| and |init| messages, and are deallocated 39// in a memory-managed environment when their retain counts drop to 0 by 40// sending |release| messages. 41template<typename Type> 42struct DefaultSingletonObjCTraits : public DefaultSingletonTraits<Type> { 43 static Type* New() { 44 return [[Type alloc] init]; 45 } 46 47 static void Delete(Type* object) { 48 [object release]; 49 } 50}; 51 52// Exactly like Singleton, but without the DefaultSingletonObjCTraits as the 53// default trait class. This makes it straightforward for Objective-C++ code 54// to hold Objective-C objects as singletons. 55template<typename Type, 56 typename Traits = DefaultSingletonObjCTraits<Type>, 57 typename DifferentiatingType = Type> 58class SingletonObjC : public Singleton<Type, Traits, DifferentiatingType> { 59}; 60 61#endif // BASE_MEMORY_SINGLETON_OBJC_H_ 62