Objective-C Singleton implementation using Grand Central Dispatch (GCD) framework

SingletonObject.h

#import <Foundation/Foundation.h>

@interface SingletonObject : NSObject

+ (id)sharedInstance;

@end

SingletonObject.m

#import "SingletonObject.h"

@implementation SingletonObject

+ (id)sharedInstance
{
	static dispatch_once_t onceToken;
	static id sharedInstance;
	
	dispatch_once(&onceToken, ^{
		sharedInstance = [[self alloc] init];
	});
	
	return sharedInstance;
}

@end