UIViewController containment like a pro

I’m going to share with you a very annoying problem I had when implementing my cool custom view controller animated container.

I wanted to create a “tabbed navigation bar” that will animate the appearance / disappearance of a UIViewController when clicking on the tabs¹. Something like this -

I won’t dig into the details of how I actually created the container view and implemented the animation but it’s not very hard (I’ll probably post about it later). The required steps are to implement your own UIViewController and use addChildViewController to display the wanted view controller, like this -

After executing this code everything seems to work, the container behaved and animated nicely but during the QA session we noticed that the contained view controllers were a bit broken. The two view controllers we used inherited from UITableViewController so they got a scrollable UITableView, we noticed that after one “cycle” of animation (switching between the tabs) the UITableView frame overflowed.

This video will probably explain it better than I did -

My immediate thought was “what the hell did I do wrong?” so I began my journey of finding an answer to custom view controller containment failures. I came upon some cool stackoverflow.com answers² but nothing fixed the problem I had, I succumbed to a quick and dirty hack that included changing the UITableView frame on viewWillAppear: - this abomination introduced a different bug in another part of the application.

After crying secretly for a bit I really wanted to nail this so I re-read Apple’s guide about custom view-contoller containment¹, and vuala the answer smacked me in the face -

Can you guess what I did wrong?

…

You guessed it right, I forgot to set my child view controller frame after adding it :(. One of the responsibilities of a container view controller is to resize the added sub views, after adding that missing piece of code everything started working perfectly :)

So what did I learn from this? Customization can be a pain, but the result is definitely worth it (and the zillion bugs that are created in the process).

Cy’a around.

Guti.