UIViewController Retaining in ARC

Question

I have a subclass of UIViewController -> MyPopUpViewController

@protocol MyPopUpViewController Delegate;
@interface MyPopUpViewController : UIViewController
{

}
@property (nonatomic, strong) id <MyPopUpViewControllerDelegate>  delegate;

-(IBAction) buttonPressed:(id)sender;
@end

@protocol MyPopUpViewControllerDelegate
-(void) popupButtonPressed: (MyPopUpViewController*)controller;
@end

I cannot have this MyPopUpViewController as an instance variable because this comes externally, and there could be many and multiple of these popups can be up. So far I tried this, and it crashes on the delegate call due to not being retained:

MyMainViewController:

-(void)externalNotificationReceived: (NSString*) sentMessage
{    
    MyPopUpViewController *popupView = [[MyPopUpViewController alloc] init];
    popupView.delegate = self;

    [self.view addSubview:popupView.view];

    [popupView setInfo :sentMessage :@"View" :@"Okay"];
    popupView.view.frame = CGRectMake(0, -568, 320, 568);
    popupView.view.center = self.view.center;
}

-(void)popupButtonPressed:(MyPopUpViewController *)controller :(int)sentButtonNumber
{
    NSLog(@"Popup Delegate Called");

    [controller.view removeFromSuperview];
    controller.delegate = nil;
    controller = nil;
}

Once the popup comes up, and when the ok button is tapped, it crashes and never gets to that NSLog. How can I change

MyPopUpViewController *popupView = [[MyPopUpViewController alloc] init];

..so it would retain without making it an instance variable?

Thanks in advance.

I doubt with this line `[popupView setInfo :sentMessage :@"View" :@"Okay"];` — βhargavḯ, Dec 06 '13 at 03:59
Yea... that line is probably problematic. But also... how does `MyPopUpViewController.m` look? Specifically, the method in which you're calling `popupButtonPressed:` on the delegate? — nhgrif, Dec 06 '13 at 04:00
@nhgrif There is nothing wrong with the `setInfo:::` method other than the horrible name. — rmaddy, Dec 06 '13 at 04:02

score 3 · Accepted Answer · answered Dec 06 '13 at 04:01

You should be doing proper view controller containment by calling addChildViewController:.

- (void)externalNotificationReceived: (NSString*) sentMessage {    
    MyPopUpViewController *popupView = [[MyPopUpViewController alloc] init];
    popupView.delegate = self;

    [popupView setInfo :sentMessage :@"View" :@"Okay"];
    popupView.view.frame = CGRectMake(0, -568, 320, 568);
    popupView.view.center = self.view.center;

    [self addChildViewController:popupView];    
    [self.view addSubview:popupView.view];
    [popupView didMoveToParentViewController:self];
}

This will keep a proper reference to the view controller as well as properly pass various view controller events. Read about this in the docs for UIViewController and the "View Controller Programming Guide for iOS".

BTW - you should name your methods better. Example:

popupButtonPressed::

should be named:

popupButtonPressed:buttonNumber:

I voted in favour of this answer for the `addChildViewController:` comment, then got to the BTW and wished I could vote again. Proper method naming is essential. — Tommy, Dec 06 '13 at 04:05
WORKS GREAT! Thank you. What's the proper way to remove the view and it's view controller in delegate? — Gizmodo, Dec 06 '13 at 05:35

score 1 · Answer 2 · answered Dec 16 '13 at 19:30

Usually delegates are weak-referenced instead of strong. I, myself, would name it something else as to not confuse other people.

Also, the following bit of code will have no effect:

-(void)popupButtonPressed:(MyPopUpViewController *)controller :(int)sentButtonNumber
{
    ...
    controller = nil;
}

the controller would be released (set to nil) automatically at the end of the scope.

UIViewController Retaining in ARC

2 Answers2