Make view property weak in ViewStateMachine to avoid retain cycle

[Ezor]

Hi,

When using ViewStateMachine standalone like the following example, I experienced a retain cycle caused by the fact that ViewStateMachine hold a strong reference on the backed view. Using a weak property fixed the problem.

class StateView: UIView {

    private var stateMachine: ViewStateMachine!
    private var loadingView: LoadingView!

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setupStateMachine()
    }

    override init(frame: CGRect) {
        super.init(frame: CGRect.zero)
        setupStateMachine()
    }

    private func setupStateMachine() {
        stateMachine = ViewStateMachine(view: self) // retain cycle
        loadingView = LoadingView(frame: self.bounds)
        stateMachine["loading"] = loadingView
    }

    func startLoading(_ message: String) {
        loadingView.label.text = message
        stateMachine.transitionToState(.view("loading"), animated: false, completion: nil)
    }

    ....
}