CODEWITHSUNDEEP
swiftuipangesturerecognizer
Alex A
Alex A

Reputation: 309

why is my gestureRecognizer returning nil?

I have tried to combine numerous tutorials to try and make a gesture recognizer start an animation on a tableView once a gesture is received on a mapView (shrinking table once map is moved like the old uber app). The animation functions, however once the animation is finished i am receiving "unexpectedly found nil when unwrapping an optional" - however it seems like it should not be nil, obviously it is, i just dont understand how. The error is 3/4 the way down, ive tried to reduce as much code as possible so parts are missing. My guess is that i have created 2 gesture recognizers which is causing the issue, but i am unsure how to combine them. Here is the code:

    class RestaurantsVC: UIViewController, MKMapViewDelegate, CLLocationManagerDelegate, UIGestureRecognizerDelegate {

    var animator: UIViewPropertyAnimator?
    var currentState: AnimationState!
    var thumbnailFrame: CGRect!
    var panGestureRecognizer: UIPanGestureRecognizer!

    override func viewDidLoad() {
        super.viewDidLoad()

        let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(RestaurantsVC.handlePan(gestureRecognizer:)))
        panGestureRecognizer.delegate = self
        self.mapView.addGestureRecognizer(panGestureRecognizer)
}

    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        return true
    }


    @objc func handlePan (gestureRecognizer: UIPanGestureRecognizer) {
        let translation = gestureRecognizer.translation(in: self.view.superview)

        switch gestureRecognizer.state {
        case .began:
            startPanning()
            animator?.startAnimation()
        case .ended:
            let velocity = gestureRecognizer.velocity(in: self.view.superview)
            endAnimation(translation: translation, velocity: velocity)
        default:
            print("Something went wrong handlePan")
        }
    }


    func startPanning() {
        var finalFrame:CGRect = CGRect()
        switch currentState {
           // code
        }
        animator = UIViewPropertyAnimator(duration: 1, dampingRatio: 0.8, animations: {
        })
    }


    func endAnimation (translation:CGPoint, velocity:CGPoint) {

            if let animator = self.animator {
                self.panGestureRecognizer.isEnabled = false //(this line is where i get the error)//

                switch self.currentState {
                case .thumbnail:
                        animator.isReversed = false
                        animator.addCompletion({ _ in
                            self.currentState = .minimized
                            self.panGestureRecognizer.isEnabled = true
                        })
                case .minimized:
                        animator.isReversed = true
                        animator.addCompletion({ _ in
                            self.currentState = .thumbnail
                            self.panGestureRecognizer.isEnabled = true
                        })
                default:
                    print("unknown state")
                }
            }
    }
}

Upvotes: 1

Views: 803

Answers (2)

drfear
drfear

Reputation: 121

This could work still without storing a reference to the gesture recognizer. You could pass the values from the gesture recognizer passed into handlePan into startAnimation and endAnimation. This would reduce the need to have superfluous properties on your class

Upvotes: 0

Craig Otis
Craig Otis

Reputation: 32054

It's nil because you're never actually assigning it.

In your viewDidLoad() function, you're actually redefining a local variable which shadows the instance variable:

let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(RestaurantsVC.handlePan(gestureRecognizer:)))
^ The 'let' keyword is redefining this variable at the local scope

You should remove the let declaration, and instead assign this as:

self.panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(RestaurantsVC.handlePan(gestureRecognizer:)))

Upvotes: 2

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