Transform a view by dragging its edge (Swift) - swift

Question

I try to make an app where the user can draw or add an arrow, and transform this arrow (translate, rotate, ...).
For the moment, I manage to draw the arrow and make all the transformations on it, but what I would like to do now is to be able to modify the arrow by dragging its edges.
To draw an arrow, I just create a UIView with a height of 20px (it is the thickness of the arrow), and a width of 400 (length of the arrow).
func drawArrow(frame: CGRect) {
let thicknessArrow = 20
let viewHorizontalArrow = UIView()
viewHorizontalArrow.frame.origin = CGPoint(x: 100, y: 600)
viewHorizontalArrow.frame.size = CGSize(width: 400, height: thicknessArrow)
drawDoubleArrow(viewHorizontalArrow, startPoint: CGPoint(x: 0, y: thicknessViewWithArrow/2), endPoint: CGPoint(x: viewHorizontalArrow.frame.width, y: thicknessViewWithArrow/2), lineWidth: 10, color: UIColor.blackColor())
}
After that, I transform the UIView thanks to the pan, pinch and rotate gesture.
The function "drawDoubleArrow" create an arrow with BezierPath and add it to the layer of the UIView.
I hope these explanations are clear enough :).
Could you help me to find a solution ?
Thanks !

Answer 1

UIBezierPath on it's own cannot easily be manipulated by gestures because it doesn't recognize them. But a UIView can recognize gestures. Combined with a CALayer's ability to be transformed and it's hitTest() method, I think you can achieve what you want.
// I'm declaring the layer as a shape layer, but depending on how your error thick is, you may need a rectangular one
let panGesture = UIPanGestureRecognizer()
var myLayer = CAShapeLayer()
viewDidLoad:
// I'm assuming you've created myBezierPath, an arrow path
myLayer.path = myBezierPath.cgPath
// Adding the pan gesture to the view's controller
panGesture.addTarget(self, action: #selector(moveLayer))
self.addGestureRecognizer(panGesture)
moveLayer:
func moveLayer(_ recognizer:UIPanGestureRecognizer) {
let p = recognizer.location(in: self)
// You will want to loop through all the layers you wish to transform
if myLayer.hitTest(p) != nil {
myLayer.position = p
}
}