how to set cornerRadius for only bottom-left,bottom-right and top-left corner textview?

(swift 4/iOS 11) Just simply say for bottom:

yourView.clipsToBounds = true 
yourView.layer.cornerRadius = 10
yourView.layer.maskedCorners = [.layerMaxXMaxYCorner, .layerMinXMaxYCorner]

for Up:

yourView.clipsToBounds = true 
yourView.layer.cornerRadius = 10
yourView.layer.maskedCorners = [.layerMaxXMinYCorner, .layerMinXMinYCorner]

in your case:

yourView.layer.maskedCorners = [.layerMaxXMaxYCorner, .layerMinXMaxYCorner, .layerMinXMinYCorner]

Hope this help :)

You just need to mask the layer as shown below:

For Swift 3:

let rectShape = CAShapeLayer()
rectShape.bounds = self.myView.frame
rectShape.position = self.myView.center
rectShape.path = UIBezierPath(roundedRect: self.myView.bounds, byRoundingCorners: [.bottomLeft , .bottomRight , .topLeft], cornerRadii: CGSize(width: 20, height: 20)).cgPath

self.myView.layer.backgroundColor = UIColor.green.cgColor
//Here I'm masking the textView's layer with rectShape layer
self.myView.layer.mask = rectShape

Lower Version:

let rectShape = CAShapeLayer()
rectShape.bounds = self.myView.frame
rectShape.position = self.myView.center
rectShape.path = UIBezierPath(roundedRect: self.myView.bounds, byRoundingCorners: .BottomLeft | .BottomRight | .TopLeft, cornerRadii: CGSize(width: 20, height: 20)).CGPath

self.myView.layer.backgroundColor = UIColor.greenColor().CGColor
//Here I'm masking the textView's layer with rectShape layer
self.myView.layer.mask = rectShape

Swift 3

extension UIView {
    func roundCorners(_ corners:UIRectCorner, radius: CGFloat) {
    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
  }
}

Use like this

YourView.roundCorners([.topLeft, .bottomLeft], radius: 10)