[iOS][swift]UIView顏色漸層

class GradientView: UIView {
    
    private var gradientLayer = CAGradientLayer()
    private var vertical: Bool = false
    
    func draw(_ colors: [Any]? , isVertical : Bool, locations: [NSNumber]? = [0.0, 1.0]) {
        self.vertical = isVertical
        
        //fill view with gradient layer
        gradientLayer.frame = self.bounds
        
        //style and insert layer if not already inserted
        if gradientLayer.superlayer == nil {
            
            gradientLayer.startPoint = CGPoint(x: 0, y: 0)
            gradientLayer.endPoint = vertical ? CGPoint(x: 0, y: 1) : CGPoint(x: 1, y: 0)
            gradientLayer.colors = colors//[UIColor.green.cgColor, UIColor.red.cgColor]
            gradientLayer.locations = locations
            
            self.layer.insertSublayer(gradientLayer, at: 0)
        }
    }
    
}