// View to hold the CAGradientLayer.
let view: UIView = UIView(frame: CGRect(x: 0, y: 0, width: 320, height: 320))
// Initialize gradient layer.
let gradientLayer: CAGradientLayer = CAGradientLayer()
// Set frame of gradient layer.
gradientLayer.frame = view.bounds
// Color at the top of the gradient.
let topColor: CGColor = UIColor.greenColor().CGColor
// Color at the middle of the gradient.
let middleColor: CGColor = UIColor.blueColor().CGColor
// Color at the bottom of the gradient.
let bottomColor: CGColor = UIColor.blackColor().CGColor
// Set colors.
gradientLayer.colors = [topColor, middleColor, bottomColor]
// Set start point.
gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)
// Set end point.
gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)
// Insert gradient layer into view's layer heirarchy.
view.layer.insertSublayer(gradientLayer, atIndex: 0)
Result :