“viewWillTransitionToSize:” not called in iOS 9 when the view controller is presented modally

Question

I present a view controller from another one:

- (void)showModalView
{
   UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
   MySecViewController *mySecViewController = [storyboard instantiateViewControllerWithIdentifier:@"secController"];
   mySecViewController.delegate = self;
   [self presentViewController:mySecViewController animated:YES completion:nil];
}

Then in the presented UIViewController, the method viewWillTransitionToSize:withTransitionCoordinator: is called in iOS 8 but not in iOS 9...

Thanks

Answer 1

In your current view controller, if you override viewWillTransitionToSize:withTransitionCoordinator:, make sure you call super. Otherwise, this message won't get propagated to children view controllers.

For Objective-C:

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];

    // Your other code ... 

And Swift:

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
    super.viewWillTransition(to: size, with: coordinator)

    // Your other code ...
}

Answer 2

May seem a trivial case, but when using an iPad check that the user has not activated rotation lock in the settings or control panel or side button

Answer 3

People have already explained that you have to call super. I'd like to add a piece of information that might help people who would have faced what i faced.

Scenario: Parent -> Child (viewWillTransition not called in child)

---

If your view controller is a child view controller, then check if the parent view controller delegate is called and if super is called there. Otherwise it won't be propagated to the child view controller!

class ParentViewController: UIViewController {

    func presentChild() {
        let child = ChildViewController()
        present(child, animated: false, compeltion: nil)
    }

    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        super.viewWillTransition(to: size, with: coordinator) // If this line is missing your child will not get the delegate call in it's viewWillTransition

        // Do something
    }
}

class ChildViewController: UIViewController {

    // This method will not get called if presented from parent view controller and super is not called inside the viewViewWillTransition available there.
    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
       super.viewWillTransition(to: size, with: coordinator)

       //Do something
    }
}

P.S - This happened to me because i did not write the code for the parent.

Answer 4

Maybe it's a little late, but I put this here for anyone stumbling upon this frustrating issue.

Keep in mind that viewWillTransitionToSize:withTransitionCoordinator: sometimes gets called on the presentingViewController of the view controller you are expecting it to. (And if that view controller has a presentingViewController too, it may get called on that)

I couldn't really figure out the logic behind this, but that was the point in my case. So I had to override viewWillTransitionToSize:withTransitionCoordinator: in many of my view controllers like this:

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];

    [self.presentedViewController viewWillTransitionToSize:size withTransitionCoordinator:coordinator];
}