Question

Im new to Objective-C & iOS programming so Im very confused about event and action handling. I don’t really understand what is the difference between connecting a button in Interface builder with its files owner method (for instance connecting button action pressed with my personal method buttonClicked) and on the other hand creating a delegate which will respond to button events? I am confused because I come from C# (.NET) and there you only handling events via delegation.

Answer 1

Let’s create event handling programmatically first. Some assumptions …

• you have class MyViewController
• this class does contain property myButton (UIButton *)
• you do want to handle events in this class

First step is to create method to handle your button taps:

-(void)onMyButtonTap:(UIButton *)sender {
  // My button was tapped, whoa, which one is in sender argument
}

Add tap event handling:

-(void)loadView {
  [super loadView];
  [self.myButton addTarget:self action:@selector(onMyButtonTap:) forControlEvents: UIControlEventTouchUpInside];
}

What this code does? self in this case is instance of MyViewController class, which is going to handle touch up inside event (addTarget). action is method which will be called when UIControlEventTouchUpInside fires.

So the addTarget:... line adds event handling and when the control event fires, this …

[self onMyButtonTap:self.myButton];

… will be called automatically.

It’s simplified example, it can be more complicated in the real world:

• you can have UIButton in separate UIView (good practice, I dislike when people put them in UIViewController)
• you can handle multiple buttons taps in one method (distinguish between them by sender argument)
• you can create more tap handling methods, one method for one button,
• …

And now back to outlets. Outlet is just an automatic glue for addTarget:....

UIButton is subclass of UIControl and here you can see how other events can be handled and what events you can handle.

Delegation is also common practice, but not for UIControl. There’s no delegate, etc. You have to do it in this way.

Or you can enhance UIButton to handle events via blocks for example. Here’s one way https://gist.github.com/2468899 or you can Google for more.