UISwipeGestureRecognizer Swipe length

In Swift

 override func viewDidLoad() {
    super.viewDidLoad()

    // add your pan recognizer to your desired view
    let panRecognizer = UIPanGestureRecognizer(target: self, action:  #selector(panedView))
    self.view.addGestureRecognizer(panRecognizer)

}

   @objc func panedView(sender:UIPanGestureRecognizer){
        var startLocation = CGPoint()
        //UIGestureRecognizerState has been renamed to UIGestureRecognizer.State in Swift 4
        if (sender.state == UIGestureRecognizer.State.began) {
            startLocation = sender.location(in: self.view)
        }
        else if (sender.state == UIGestureRecognizer.State.ended) {
            let stopLocation = sender.location(in: self.view)
            let dx = stopLocation.x - startLocation.x;
            let dy = stopLocation.y - startLocation.y;
            let distance = sqrt(dx*dx + dy*dy );
            NSLog("Distance: %f", distance);

        if distance > 400 {
            //do what you want to do
        }
    }
}

Hope that helps all you Swift pioneers

It's impossible to get a distance from a swipe gesture, because the SwipeGesture triggers the method where you could access the location exactly one time, when the gesture has ended.
Maybe you want to use a UIPanGestureRecognizer.

If it possible for you to use pan gesture you would save the starting point of the pan, and if the pan has ended calculate the distance.

- (void)panGesture:(UIPanGestureRecognizer *)sender {
    if (sender.state == UIGestureRecognizerStateBegan) {
        startLocation = [sender locationInView:self.view];
    }
    else if (sender.state == UIGestureRecognizerStateEnded) {
        CGPoint stopLocation = [sender locationInView:self.view];
        CGFloat dx = stopLocation.x - startLocation.x;
        CGFloat dy = stopLocation.y - startLocation.y;
        CGFloat distance = sqrt(dx*dx + dy*dy );
        NSLog(@"Distance: %f", distance);
    }
}