Swift change layer colour - ios

Question

Currently in my app when user tap on the screen a red dot will appear at wherever the user touch if a user tap on the screen multiple times there will be multiple dot. I want to add a feature to allow user to change the colour.
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
if let touch = touches.first as UITouch?{
let location = (touch as! UITouch).location(in: self.imageView)
let layer = CAShapeLayer()
layer.path = UIBezierPath(roundedRect: CGRect(x: location.x, y: location.y, width: 2, height: 2), cornerRadius: 50).cgPath
layer.fillColor = UIColor.red.cgColor
imageView.layer.addSublayer(layer)
}
}
When I tried the following method I am able to change the colour but for some reason no matter how many times I've tap on the screen there will only be one dot. My guess is that every time I tap on my screen a new layer will be created and it will replace the old layer. is there anyway I can allow user to change the colour of the layer while keeping all of dots that is already on the layer?
class ViewController: UIViewController,UIScrollViewDelegate {
let layer = CAShapeLayer()
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
if let touch = touches.first as UITouch?{
let location = (touch as! UITouch).location(in: self.imageView)
layer.path = UIBezierPath(roundedRect: CGRect(x: location.x, y: location.y, width: 2, height: 2), cornerRadius: 50).cgPath
layer.fillColor = UIColor.red.cgColor
imageView.layer.addSublayer(layer)
}
}
#IBAction func changecolorBtn(_ sender: Any) {
layer.fillColor = UIColor.green.cgColor
}
}

Answer 1

Because of you used only one layer
let layer = CAShapeLayer()
and whenever you set
layer.path = UIBezierPath(roundedRect: CGRect(x: location.x, y: location.y, width: 2, height: 2), cornerRadius: 50).cgPath
It will remove the old path, and your new path has only one point.
That's why
When I tried the following method I am able to change the colour but for some reason no matter how many times I've tap on the screen there will only be one dot.
You can simple fix you issue by combine all your dot path. Like this
// add the combine path as your global variable
let layer = CAShapeLayer()
let combinePath = CGMutablePath()
and change your add path code
layer.path = UIBezierPath(roundedRect: CGRect(x: location.x, y: location.y, width: 2, height: 2), cornerRadius: 50).cgPath
to add the combine path
let path = UIBezierPath(roundedRect: CGRect(x: location.x, y: location.y, width: 2, height: 2), cornerRadius: 50).cgPath
combinePath.addPath(path)
layer.path = combinePath