Gradient of UIButton is not showing - ios

Question

I’m trying to put a gradient on a button, but it is not showing up. All the other button parts are working and displaying perfectly!
Function that creates the button
private func createButtonMenu(buttonTitle: String, buttonIcon: UIImage, colorOne: UIColor, colorTwo: UIColor) -> UIButton{
let button = UIButton()
button.setTitle(buttonTitle, for: .normal)
button.translatesAutoresizingMaskIntoConstraints = false
button.contentHorizontalAlignment = .leading
button.contentVerticalAlignment = .bottom
button.contentEdgeInsets = UIEdgeInsets(top: 0, left: 10, bottom: 10, right: 0)
button.layer.cornerRadius = 30
button.layer.masksToBounds = true
let icon = UIImageView(image: buttonIcon)
icon.translatesAutoresizingMaskIntoConstraints = false
button.addSubview(icon)
button.heightAnchor.constraint(equalToConstant: 100).isActive = true
icon.topAnchor.constraint(equalTo: button.topAnchor, constant: 10).isActive = true
icon.leadingAnchor.constraint(equalTo: button.leadingAnchor, constant: 10).isActive = true
let gradientLayer = CAGradientLayer()
gradientLayer.frame = button.bounds
gradientLayer.colors = [UIColor.red, UIColor.blue]
gradientLayer.locations = [0.0, 1.0]
gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)
gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)
button.layer.insertSublayer(gradientLayer, at: 0)
//button.backgroundColor = .red
icon.widthAnchor.constraint(equalToConstant: 30).isActive = true
icon.heightAnchor.constraint(equalToConstant: 30).isActive = true
return button
}
Function that inserts the button in view
private func configuringButtons(){
//Creating buttons
let userButtonMenu: UIButton = createButtonMenu(buttonTitle: "009", buttonIcon: #imageLiteral(resourceName: "woman"), colorOne: .red, colorTwo: .blue)
view.addSubview(userButtonMenu)
}

Answer 1

Colours in a gradient layer must be of type CGColor, not UIColor.
gradientLayer.colors = [UIColor.red.cgColor, UIColor.blue.cgColor]