使用面膜，使UIButton的文本透明斯威夫特4

我有一點麻煩搞清楚如何使UIButton標題透明的，使得它的顏色是上海華盈的漸變背景的顏色。使用面膜，使UIButton的文本透明斯威夫特4

我已經看到了有關呈現的按鈕圖像線程，但它是在Objective-C與舊的CG API，我想知道如果有人能在一個更好的辦法來解決這個問題提出建議。

任何意見將不勝感激！

這是我到目前爲止有：

import UIKit 
import Foundation 

class MainViewController: UIViewController { 

    let headingLabel: UILabel = { 
     let label = UILabel() 
     label.text = "Hello, World" 
     label.font = label.font.withSize(30) 
     label.textColor = .white 
     label.textAlignment = .center 
     label.translatesAutoresizingMaskIntoConstraints = false 
     return label 
    }() 

    let continueButton: UIButton = { 
     let button = UIButton() 
     button.setTitleColor(.black, for: .normal) 
     button.setTitle("Continue", for: .normal) 
     button.layer.cornerRadius = 10 
     button.backgroundColor = .white 
     button.translatesAutoresizingMaskIntoConstraints = false 
     return button 
    }() 

    let gradientLayer: CAGradientLayer = { 
     let layer = CAGradientLayer() 
     layer.colors = [ 
      UIColor(red: 96/255, green: 165/255, blue: 238/255, alpha: 1.0).cgColor, 
      UIColor(red: 233/255, green: 97/255, blue: 99/255, alpha: 1.0).cgColor, 
     ] 
     layer.startPoint = CGPoint(x: 0.0, y: 0.0) 
     layer.endPoint = CGPoint(x: 1.0, y: 1.0) 
     return layer 
    }() 

    override func viewDidLoad() { 
     super.viewDidLoad() 
     setupView() 
    } 

    override var preferredStatusBarStyle: UIStatusBarStyle { 
     return .lightContent 
    } 

    override func viewDidAppear(_ animated: Bool) { 
     navigationController?.navigationBar.isHidden = true 
    } 

    func setupView() { 
     // root view 
     gradientLayer.frame = view.frame 
     view.layer.addSublayer(gradientLayer) 
     view.addSubview(headingLabel) 
     view.addSubview(continueButton) 

     // constraints 
     let views: [String: UIView] = [ 
      "headingLabel": headingLabel, 
      "continueButton": continueButton, 
      "superview": view 
     ] 

     var constraints: [NSLayoutConstraint] = [] 

     let verticalHeadingLabelConstraint = NSLayoutConstraint.constraints(withVisualFormat: 
      "V:|-100-[headingLabel(30)]", 
      options: [], 
      metrics: nil, 
      views: views) 
     constraints += verticalHeadingLabelConstraint 

     let horizontalHeadingLabelConstraint = NSLayoutConstraint.constraints(withVisualFormat: 
      "H:|-[headingLabel]-|", 
      options: .alignAllCenterX, 
      metrics: nil, 
      views: views) 
     constraints += horizontalHeadingLabelConstraint 

     let verticalContinueButtonConstraint = NSLayoutConstraint.constraints(withVisualFormat: 
      "V:[continueButton(50)]-100-|", 
      options: [], 
      metrics: nil, 
      views: views) 
     constraints += verticalContinueButtonConstraint 

     let horizontalContinueButtonConstraint = NSLayoutConstraint.constraints(withVisualFormat: 
      "H:|-100-[continueButton]-100-|", 
      options: [], 
      metrics: nil, 
      views: views) 
     constraints += horizontalContinueButtonConstraint 

     view.addConstraints(constraints) 
    } 

}