Singleton in Interface Builder.

gistfile1.m

+ (instancetype)handler
{
    __strong static id *_sharedInstance = nil;
    static dispatch_once_t onlyOnce;
    dispatch_once(&onlyOnce, ^{
        _sharedInstance = [[self _alloc] _init];
    });
    return _sharedInstance;
}

+ (id) allocWithZone:(NSZone*)z
{
    return [self handler];
}

+ (id) alloc
{
    return [self handler];
}

- (id) init
{
    return  self;
}

+ (id)_alloc
{
    return [super allocWithZone:NULL];
}

- (id)_init
{
    self = [super init];
    if (self) {
        // Common setup
    }
    return self;
}

__strong static id *_sharedInstance = nil; should be id _sharedInstance without a *.

@chbeer thank you, I missed that typo