How to create rounded UIButton with top-left & bottom-left corner radius only

Question

I need to create a button with top-left & bottom-left corner radius like this one . I tried by creating the following extension that was taken from one of stackoverflow answer:

extension UIButton {

   func roundCorners(corners:UIRectCorner, radius: CGFloat) {
       self.layer.borderColor = GenerateShape.UIColorFromHex(0x989898, alpha: (1.0-0.3)).CGColor
       self.layer.borderWidth = 1.0
       let path = UIBezierPath(roundedRect: self.bounds, byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: radius))
       let mask = CAShapeLayer()
       mask.path = path.CGPath
       self.layer.mask = mask

   }
}

then called the method like this:

self.collectionBtn.roundCorners(.TopLeft | .BottomLeft, radius: cornerRadius) 

this code generates the following shape

So why the top-left & bottom-left corner invisible? What should I do to make them visible?

Answer 1

Your code is applying a mask layer to your button. that causes anything outside the shape you install in the mask layer to be masked away. When you install a path with rounded corners, it essentially "shaves off" the 2 corners. That's not what you want.

You probably want to create a shape layer and install it as a regular sublayer of your button's layer, not as the mask layer. You'll need to set the fill color to clear however.

Change your code like this:

extension UIButton 
{
  func roundCorners(corners:UIRectCorner, radius: CGFloat) 
  {
    let borderLayer = CAShapeLayer()
    borderLayer.frame = self.layer.bounds
    borderLayer.strokeColor = GenerateShape.UIColorFromHex(0x989898, 
      alpha: (1.0-0.3)).CGColor
    borderLayer.fillColor = UIColor.clearColor().CGColor
    borderLayer.lineWidth = 1.0
    let path = UIBezierPath(roundedRect: self.bounds, 
      byRoundingCorners: corners, 
      cornerRadii: CGSize(width: radius, height: radius))
    borderLayer.path = path.CGPath
    self.layer.addSublayer(borderLayer);
  }
}

EDIT:

Your syntax for setting the corners won't work in Swift 2:

self.collectionBtn.roundCorners(.TopLeft | .BottomLeft, radius: 10)

Should be

self.collectionBtn.roundCorners([.TopLeft, .BottomLeft], radius: 10)