Dismissing a Presented View Controller

In addition to Michael Enriquez's answer, I can think of one other reason why this may be a good way to protect yourself from an undetermined state:

Say ViewControllerA presents ViewControllerB modally. But, since you may not have written the code for ViewControllerA you aren't aware of the lifecycle of ViewControllerA. It may dismiss 5 seconds (say) after presenting your view controller, ViewControllerB.

In this case, if you were simply using `dismissViewController` from ViewControllerB to dismiss itself, you would end up in an undefined state--perhaps not a crash or a black screen but an undefined state from your point of view.

If, instead, you were using the delegate pattern, you would be aware of the state of ViewControllerB and you can program for a case like the one I described.

Swift

let rootViewController:UIViewController = (UIApplication.shared.keyWindow?.rootViewController)!

if (rootViewController.presentedViewController != nil) {
rootViewController.dismiss(animated: true, completion: {
//completion block.
})
}

I think Apple are covering their backs a little here for a potentially kludgy piece of API.

[self dismissViewControllerAnimated:NO completion:nil]

Is actually a bit of a fiddle. Although you can - legitimately - call this on the presented view controller, all it does is forward the message on to the presenting view controller. If you want to do anything over and above just dismissing the VC, you will need to know this, and you need to treat it much the same way as a delegate method - as that's pretty much what it is, a baked-in somewhat inflexible delegate method.

Perhaps they've come across loads of bad code by people not really understanding how this is put together, hence their caution.

But of course, if all you need to do is dismiss the thing, go ahead.

My own approach is a compromise, at least it reminds me what is going on:

[[self presentingViewController] dismissViewControllerAnimated:NO completion:nil]


_[Swift]_

self.presentingViewController?.dismiss(animated: false, completion:nil)

I like this one:

(viewController.navigationController?.presentingViewController
?? viewController.presentingViewController
?? viewController).dismiss(animated: true)

Focusing on the question's title only, this is the right answer.

presentedViewController?.dismiss(animated: true)