Correct time to call viewDidAppear manually?

Question

I have a UITableViewController in my app, which is added to the view hierarchy directly. After the view appears, I want to scroll to a specific cell. My solution would be to call the code for scrolling in -[viewDidAppear].

According to Apple's docs I have to call the method manually:

If the view belonging to a view controller is added to a view hierarchy directly, the view controller will not receive this message. If you insert or add a view to the view hierarchy, and it has a view controller, you should send the associated view controller this message directly.

The question is: When is the right time to call it manually?

Calling it from the parent view controller's -[viewDidAppear] leads to a crash when I try to do the scrolling because apparently, the table view actually didn't yet appear and therefore thinks it has no sections to scroll to.

Answer 1

If you are using view controller containment don't call viewWillAppear: directly. Instead use – beginAppearanceTransition:animated: and – endAppearanceTransition.

If you are implementing a custom container controller, use this method to tell the child that its views are about to appear or disappear. Do not invoke viewWillAppear:, viewWillDisappear:, viewDidAppear:, or viewDidDisappear: directly.

Calling addSubView will automatically trigger viewWillAppear: and viewDidAppear: if the view's viewController is a child view controller, therefore calling viewWillAppear: directly will trigger view will appearance method twice. Using beginAppearanceTransition:animated:and– endAppearanceTransition` will suppress the automatic behaviour so you only get it called once.