CODEWITHSUNDEEP
iphoneiosuiviewcontroller
hpique
hpique

Reputation: 120324

Nesting UIViewControllers in iOS

Consider a UIViewController whose view contains the view of another UIViewController.

Is it correct to say that the parent UIViewController is responsible to call the lifecycle methods of the child controller? Methods such as:

- (void)viewWillAppear:(BOOL)animated;
- (void)viewDidAppear:(BOOL)animated;
- (void)viewWillDisappear:(BOOL)animated;
- (void)viewDidDisappear:(BOOL)animated;

For example:

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    [_childViewController viewWillAppear:animated];
}

If so, which methods must be called?

Is there a better way to do this? Clearly the above approach is not forward-compatible: if a new lifecycle method is added the parent class needs to be modified to propagate the call of the new method.

Or is nesting view controllers simply a bad idea and should be avoided?

Upvotes: 0

Views: 332

Answers (2)

Jeroen Leenarts
Jeroen Leenarts

Reputation: 532

If you want to create a hierarchy which still supports iOS 4, you would indeed need to forward the messages detailed in the documentation of the addChildViewController: yourself.

If iOS 4 is not targeted and you only need to build for ios 5 and later, stick with the new API as jrturton said.

Upvotes: 0

jrturton
jrturton

Reputation: 119242

The correct way to do this is to add the view controller as a child view controller. You need to maintain both a view hierarchy (adding the view as a subview) and a view controller hierarchy (adding the view controller as a child). All of the life cycle methods are then called for you.

The relevant methods are addChildViewController: and didMoveToParentViewController:.

There was a talk on view controller containment in WWDC 2011, I recommend watching the video.

Upvotes: 2

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