When to fetch velocity in UIPanGestureRecognizer

Question

I'm trying to get information about a gesture on main view. My main goal is to fetch start position, end position and velocity between those two. My code is as below;

override func viewDidLoad() {
        super.viewDidLoad()
        
        self.view.addGestureRecognizer(
            UIPanGestureRecognizer.init(target: self, action: #selector(self.gestureListener(recognizer:)))
        )
    }

@objc func gestureListener(recognizer: UIPanGestureRecognizer) {
        var start_x: CGFloat? = nil
        var start_y: CGFloat? = nil
        
        var end_x: CGFloat? = nil
        var end_y: CGFloat? = nil
        
        var velocity_x: CGFloat? = nil
        var velocity_y: CGFloat? = nil
        
        switch recognizer.state {
        case .began:
            let startLocation = recognizer.location(in: recognizer.view)
            start_x = startLocation.x
            start_y = startLocation.y
            break
        case .ended:
            let endLocation = recognizer.location(in: recognizer.view)
            end_x = endLocation.x
            end_y = endLocation.y
        
            let velocity = recognizer.velocity(in: recognizer.view)
        
            velocity_x = velocity.x
            velocity_y = velocity.y
            break
        case .possible:
            break
        case .changed:
            break
        case .cancelled:
            break
        case .failed:
            break
        @unknown default:
            break
 }

But i couldn't be sure if it is the right way to fetch velocity (in ended state of GestureRecognizer)

What is the difference if i get velocity out of switch case (meaning before every state). Because i saw examples like that on stackoverflow.

To explain more, what i want to achieve is something like GestureDetector's onFling() method in Android;

private class GestureListener : GestureDetector.SimpleOnGestureListener() {

            override fun onDown(e: MotionEvent): Boolean {
                return true
            }
            override fun onSingleTapUp(e: MotionEvent): Boolean {
                onClick()
                return super.onSingleTapUp(e)
            }
            override fun onDoubleTap(e: MotionEvent): Boolean {
                onDoubleClick()
                return super.onDoubleTap(e)
            }
            override fun onLongPress(e: MotionEvent) {
                onLongClick()
                super.onLongPress(e)
            }

            override fun onFling(e1: MotionEvent, e2: MotionEvent, velocityX: Float, velocityY: Float): Boolean {
                println(e1.x, e1.y, e2.x, e2.y, velocityX, velocityY) 
                return false
            }
        }

Thank you for your replies.