Question

On iOS, if we use Interface Builder, we can create Outlet and Action easily.

If we use Objective-C code instead of Interface Builder, we can create outlet quite easily too, it seems, by just

datePicker = [[UIDatePicker alloc] initWithFrame:CGRectMake(200, 200, 200, 200)];
[self.view addSubview:datePicker];

and that we define an instance variable in the .h file.

UIDatePicker *datePicker;

And I think this is exactly like an Outlet?

How about for Actions — how do we create Actions purely using Objective-C code (without using Interface Builder) for the different types of user interaction?

Answer 1

Just like this:

- (void)someMethod {
  //...
  [button_ addTarget:self
              action:@selector(buttonAction:)
    forControlEvents:UIControlEventTouchUpInside];
  //...
}

//...

// Either |IBAction| or |void| is okay,
//   the former one is just used to be shown in Interface Builder
- (void)buttonAction:(id)sender {
  // your action code here
}

Note: IBOutlet & IBAction are just for IB (short for Interface Builder). You can forget it if you don’t want to use Interface Builder to manage your views & actions.