Example of gradient on iOS

ButtonWithGradient.swift

override func draw(_ rect: CGRect) {
	self.layer.insertSublayer(AppDelegate.mainGradient(self.frame.width, self.frame.height), at: 0)
}

GradientExample.swift

static func mainGradient(_ width: CGFloat, _ height: CGFloat) -> CAGradientLayer {
	let gradient = CAGradientLayer()
    gradient.frame = CGRect(x: 0, y: 0, width: width, height: height)
    gradient.startPoint = CGPoint(x: 0, y: 1)
    gradient.endPoint = CGPoint(x: 1, y: 0)
    gradient.colors = [UIColor(rgb: 0x6441a5).cgColor,
                       UIColor(rgb: 0x2a0845).cgColor]

    return gradient
}

NavBarWithGradient.swift

override func viewDidLoad() {
	super.viewDidLoad()
	// Do any additional setup after loading the view, typically from a nib.

	// prepare navigationBar
	self.navigationController?.navigationBar.setBackgroundImage(UIImage(), for: .default)
	self.navigationController?.navigationBar.shadowImage = UIImage()
	self.navigationController?.navigationBar.isTranslucent = true
	self.navigationController?.navigationBar.backgroundColor = UIColor.clear

	// white largeTitle and statusBar
    	self.navigationController?.navigationBar.largeTitleTextAttributes = [NSAttributedStringKey.foregroundColor: UIColor.white]
	UIApplication.shared.statusBarStyle = .lightContent

	// apply gradient
	self.view.layer.addSublayer(
		AppDelegate.mainGradient(UIApplication.shared.statusBarFrame.width,
					 UIApplication.shared.statusBarFrame.height + self.navigationController!.navigationBar.frame.height))
}