viewWillAppear not invoked for subview controller

cocoa-touch, ios, uiviewcontroller

Solution

The application isn't aware of the subview's view controller if you do this, you need to introduce view controller containment to make the root view controller aware. Doing so will handle any events like this.

Because `loadView` could be called more than once pre iOS 6, I'd advise creating the view controller within `init`, and then add the subview within `loadView`. It should be like this:

- (id)init {
    ...
    self.doneButtonViewController = [[DoneButtonViewController alloc] init];
    [self addChildViewController:self.doneButtonViewController];
    [self.doneButtonViewController didMoveToParentViewController:self];
    ...
}

- (void)loadView {
    ...
    [self.view addSubview:self.doneButtonViewController.view];
    ...
}

See "Implementing a Container View Controller" at http://developer.apple.com/library/ios/#documentation/uikit/reference/UIViewController_Class/Reference/Reference.html

Problem

I have an odd case -- a view controller that creates its own view in `loadView` and which is then added to an existing view. Here is the code that creates and adds the VC: ``` self.doneButtonViewController = [[DoneButtonViewController alloc] init]; [self.view addSubview:self.doneButtonViewController.view]; ``` This code is executed in `viewDidLoad` of the "parent" VC. The odd thing is that the `viewWillAppear` method of the added VC is never invoked (nor is `viewDidAppear`), but the `viewWillDisappear` method of the added VC is invoked (at the appropriate time), just as one would expect. Any clue as to why `viewWillAppear` is not getting invoked?

Original source