Sawyer05 Sawyer05 - 6 months ago 27
Swift Question

Lazy instantiating a UIDynamicAnimator with referenceView - Swift

I'm trying to lazy instantiate a UIDynamicAnimator in my code. I want to initialise it with an UIView as an IBOutlet I have.

class ViewController: UIViewController {

@IBOutlet var gameView : UIView

@lazy var animator = UIDynamicAnimator(referenceView: gameView)
...


I'm assuming this isn't working because the UIView isn't yet created because the animator property throws back an error saying it can't find the gameView.

How can I get around this?

Answer

In the session video "Building Interruptible and Responsive Interactions", they did exactly this.

The solution is to define animator as an Optional and initialize it inside viewDidLoad.

class ViewController: UIViewController {
    var animator : UIDynamicAnimator?
    @IBOutlet var gameView : UIView
    override func viewDidLoad() {
       super.viewDidLoad()
       animator = UIDynamicAnimator(referenceView: gameView)
       animator!.property = value
       ...
    }
...

I slightly dislike this because future references to animator will all need to unwrap it.

A slightly better approach imo is to define it as an implicitly unwrapped optional. So it would look like this:

class ViewController: UIViewController {
    var animator : UIDynamicAnimator!
    @IBOutlet var gameView : UIView
    override func viewDidLoad() {
       super.viewDidLoad()
       animator = UIDynamicAnimator(referenceView: gameView)
       animator.property = value
       ...
    }
...