Cocoa Singleton implementation

ACSingleton.m

#import "ACSingleton.h"
@implementation ACSingleton

#pragma mark -
#pragma mark Singleton Pattern

static ACSingleton* _sharedInstance;
static dispatch_once_t _instanceFlag;


// Method to get the shared instance
+ (ACSingleton*)sharedInstance
{
    dispatch_once(&_instanceFlag, ^{
        _sharedInstance = [[self alloc] init];
    });
    return _sharedInstance;
}


// No copies are allowed
- (id)copyWithZone:(NSZone *)zone
{
    return [ACSingleton sharedInstance];
}



#pragma mark -
#pragma mark Initialization

// Init methode to override by subclass
- (id)init 
{
    // Prevent class from being initialized multiple times
    if (_sharedInstance) return _sharedInstance;

    self = [super init];
    if (self) {
        // Initialize iVars
    }
    return self;
}


@end