UIViewControllerAnimatedTransitioning vs custom UIStoryboardSegue

Question

Custom transitions are fairly new to me. I had to incorporate them into the last project I worked on and ended up using both the UIViewControllerAnimatedTransitioning protocol and custom segues.

Custom segues seem a bit cleaner/friendly in that you can choose them in a storyboard and be done with it. However there doesn't seem to be as-friendly way to set up a back/pop segue. I've read about unwinding segues but I can't seem to find anything around tying one to the back button of a nav controller.

The UIViewControllerAnimatedTransitioning protocol approach has a bit more set up but allows you to specify both the entering and exit of the views.

In the case of my app not being able to pop back with my custom segues wasn't an issue because the flow of the app doesn't allow you to go back to the previous views. Most applications though require this thus a custom segue seems worthless unless you subclass UINavigationController and allow for custom popping segues.

Am I missing something because it seems UIViewControllerAnimatedTransitioning is the best approach to take for animations between view controllers. Why would I ever want to subclass UIStoryboardSegue?

Answer 1

I agree that there is a lack of documentation on unwind segues compared to other types of segues, but after you get the hang of them, they are pretty straightforward. My understanding is that segues (including unwind segues) is the way that Apple intends you to transition between view controllers. Even when you create custom segues, the regular unwind segues should still function.

In my own work, I have subclassed a UIStoryboardSegue to execute a custom animation when transitioning between segues. Using a widely known app as an example, when you tap the menu button in Uber's app, the map view controller moves down, and a table view controller appears. And when you a tap a row in the table, the new view controller slides in from the right, but the map view controller is still visible on the screen. And when you tap the map view controller, it returns to its original position. For some reason, I believe that Uber actually didn't implement segues at all, but just place view controllers on top of view controllers, but I have implemented something similar in my own app with custom segues. These segues are difficult to replicate with Apple's default segues, so I used custom ones.

If you are tying an unwind segue to a back button, then you will want to override the normal unwind that comes along with the default back button in the uinavigationcontroller. I have found it very difficult to customize that segue. I would recommend hiding the default back button that comes with the uinavigationcontroller, adding your own bar button, and tying this new button to an unwind segue. I know that this is annoying, considering the default back button has some added functionality, such as using the title from the previous view controller as its text when the title is short enough. Unfortunately though, I think Apple really wants to discourage you from customizing the default button and makes it difficult to alter. I have left out how to replace the default back button with the custom one, so let me know if you have trouble.

Anyway, to create the unwind segue, you must first create a method in the class (or parent class) of the uiviewcontroller you are unwinding to (not from).

- (IBAction) methodName:(UIStoryboardSegue *)segueName

You can change the methodName and segueName to whatever you like. Now go to your storyboard, and go to the scene containing the uiviewcontroller you are unwinding from. If you now ctrl drag from this uiviewcontroller (the yellow button on the left side of the bar at the top of the controller) to the exit button (the orange button on the right side of the same bar) you will now see a menu popping up that contains the methodName above. Click that method, and your unwind segue will now be created.

After you have created the unwind segue, you now see it in the outline on the left of the storyboard. If you click the segue, you can inspect it and give it an identifier.

Now to deal with tying it to the back button...

Again, viewing the uiviewcontroller you are unwinding from , if you control drag from the custom back button (not the default back button) in the storyboard to the class of this uiviewcontroller, an IBAction will be created for you tied to the button. In this method, add in:

[self performSegueWithIdentifier: segueIdentifier sender:nil];

where segueIdentiferis the identifier you gave the unwind segue above. Now when you tap the back button, the unwind segue will be executed. You can also do some animations or what not before the unwind segue is executed.

I have actually done some complicated custom unwind segues dealing with animating both the source and destination view controllers. If you can be more specific regarding how you would like the unwinding to look, I can try to help you out.