I setup a view controller scene with interface builder. I add a view to my controller and add a custom class (CustomView) to it.
The view controller code
class ViewController: UIViewController {
    @IBOutlet var myCustomView: CustomView!
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    override func viewDidAppear(animated: Bool) {
        print(myCustomView.frame.origin)
    }
}
The question
Why the origin of myCustomView is equal to (-4.0, 64.0) and not (0, 64) ?

 
     
    