CACornerMask introduced in iOS 11, which help to define topleft, topright, bottomleft, bottom right in view layer. Below is example to use.
Here I try to rounded only two top corner:
myView.clipsToBounds = true
myView.layer.cornerRadius = 10
myView.layer.maskedCorners = [.layerMinXMinYCorner,.layerMaxXMinYCorner]
FYI Ref:
