iphone - What does [super viewWillAppear] do, and when is it required?

Question

-(void)viewWillAppear:(BOOL)animated{
//something here
[super viewWillAppear];
}

Is [super viewWillAppear]; always required? If not when and why do you use it?

Answer 1

First of all, the correct boiler plate should be:

-(void)viewWillAppear:(BOOL)animated{
   [super viewWillAppear:animated];
   //something here
}

In other words, call super first, then do your own thing. And you have to pass the animated parameter to super.

You usually want to call the super class' implementation first in any method. In many languages it's required. In Objective-C it's not, but you can easily run into trouble if you don't put it at the top of your method. (That said, I sometimes break this pattern.)

Is calling super's implementation required? In the case of this particular method you could get unexpected behavior if you don't call it (especially if you have subclassed a UINavigationController for example). So the answer is no not in a technical sense, but you should probably always do it.

However, in many other methods there may be good reasons for not calling super.