Caleb Madrigal

Programming, Hacking, Math, and Art


How to reference self in a block in Objective-C

When using ARC (automatic reference counting) in Objective-C, you need to be careful to avoid causing retain cycles. One place where a retain cycle can occur is where self is referenced in a block. To avoid a retain cycle, you can use the __unsafe_unretained modifier as such:

__unsafe_unretained id unretained_self = self;
reachability = [Reachability reachabilityWithHostname:@""];
reachability.reachableBlock = ^(Reachability *r) {
    dispatch_async(dispatch_get_main_queue(), ^{
        SurveyFormController *myself = unretained_self;
        self.mapView.reachable = YES;
        [myself configureView];