interactivePopGestureRecognizer stops working when UINavigationController's delegate is set. Why?

Question

Created May ’19

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In my code, one of the view controllers in the navigation controller's stack is setting itself as the delegate of

navigationController

in its viewDidLoad. I am doing this to provide a custom animator for the push operation. I am providing implementation only for navigationController(_:animationControllerFor:from:to:)
and nothing else.

I also ensured that I am not missing any calls to

super

in any of the overridden methods.

But the side effect of this is that the interactive pop gesture has stopped working i.e. when I perform the gesture nothing happens.

On digging deeper, I found that this is being caused by the delegate of the

interactivePopGestureRecognizer
. This delegate is system provided. I am not setting this anywhere in my code.

What I found was that when I am setting the delegate of the

navigationController

, the delegate of the

interactivePopGestureRecognizer

is blocking the gesture by returning false for func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool
.

I want to know why is this behavior happening.

Do I have to do something else to make it work? By this I mean to make it work properly i.e. the system provided delegate for

interactivePopGestureRecognizer

allows the gestures. Not by writing a workaround code.

I have also gone through Apple's documentation for UINavigationController but found nothing which can explain this issue.

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Answer 1

Macho Man Randy Savage OP

Sep ’19

It's pretty annoying. If the navigation controller delegate at any point (it seems) provides a custom animator (in my case for popping) it breaks the interactive pop gesture.

Only workaround I have to install a *temporary* delegate object that implements the transition then reset the delegate back to an object that does not implement the optional -navigationController:animationControllerForOperation:fromViewController:toViewController: when the custom transition completes.

1