cocoa touch - Is it wise to "nest" UIViewControllers inside other UIViewControllers like you would UIViews?

Question

I've got a fairly complex view, for me anyway, that has a few "trays" with custom interface items on them. They slide in and out of my root view. I'd like to nest (addSubview) the items inside the view. Each needs some setup before being displayed...and none can be configured in IB (they're subclasses of UIView).

I'm wondering if it makes sense to subclass UIViewController for each "tray" and then have the VC's view property point to the "tray" view which I can populate with my custom UIView objects. This way I can leverage the viewDidLoad, etc... methods in UIViewController.

I'm not aware of others doing this - at least in the few samples I've looked at. It would create a situation where there would be multiple view controllers being displayed on the screen at once. from the Navigation controller itself on down to the rootViewController and its view and then any number (well, screen size permitting) of these small trayViewControllers. If so, how's the responder chain work? i assume it'd go from lowest UIView to its enclosing VC, then to that VC's parent view, then that view's VC, etc. etc. repeat, repeat.. up to UIApplication... am I asking for trouble?

OR, do I just stick with UIViews and adding subviews into subviews, etc. etc..

Answer 1

Prior to iOS 5.0 this will specifically not recommended because the nested view controllers' lifecycle events – viewWillAppear, etc. –?won't be called. See Abusing UIViewControllers.

With multiple UIViewController’s views visible at once some of those controllers may not receive important messages like -viewWillAppear: or -didReceiveMemoryWarning. Additionally some of their properties like parentViewController and interfaceOrientation may not be set or updated as expected.

iOS 5.0 added containment UIViewControllers that correctly handles those lifecycle events by adding child view controllers.

- (void)addChildViewController:(UIViewController *)childController

I spent countless hours trying to get nested view controllers to work in iOS 4. I eventually did, but it required a lot of glue code that was easy to get wrong. Then I saw the warning in the docs.