The Objective-C Singleton

Below is a template for the singletons that we use in objective-c.

MySingleton.h:

#import <Foundation/Foundation.h>
 
@interfaceMySingleton :NSObject {
 
}
+(MySingleton*)sharedMySingleton;
-(void)sayHello;
@end

MySingleton.m:

@implementationMySingleton
staticMySingleton*_sharedMySingleton = nil;
 
+(MySingleton*)sharedMySingleton
{
        @synchronized([MySingleton class])
        {
                if (!_sharedMySingleton)
                        [[self alloc] init];
 
                return_sharedMySingleton;
        }
 
        return nil;
}
 
+(id)alloc
{
        @synchronized([MySingleton class])
        {
                NSAssert(_sharedMySingleton == nil, @"Attempted to allocate a second instance of asingleton.");
                _sharedMySingleton= [super alloc];
                return_sharedMySingleton;
        }
 
        return nil;
}
 
-(id)init {
        self = [super init];
        if (self != nil) {
                // initialize stuff here
        }
 
        return self;
}
 
-(void)sayHello {
        NSLog(@"HelloWorld!");
}
@end

Using themethods of the singleton is then as easy as this:

[[MySingletonsharedMySingleton] sayHello];

출처 : http://getsetgames.com/2009/08/30/the-objective-c-singleton/