Swift 3：将UIButton扩展添加到ViewController

Question

我是iOS / Swift的初学者，试图创建一个没有Storyboard的简单应用程序。我创建了一个UIButton扩展，我想在视图中添加一个简单的按钮（稍后将设置约束）。不幸的是，该按钮不可见。如果有人帮助我，我将不胜感激。谢谢！

--- Buttons.swift-

extension UIButton {

func createRectangleButton(buttonPositionX: Double, buttonPositionY: Double ,buttonWidth: Double, buttonHeight: Double, buttonTilte: String) {
    let button = UIButton(type: .system) as UIButton
    button.frame = CGRect(x: buttonPositionX, y: buttonPositionY, width: buttonWidth, height: buttonHeight)
    button.setTitle(buttonTilte, for: .normal)
    button.backgroundColor = COLOR_WHITE
    button.tintColor = COLOR_BLACK
    }   
}

-InitialViewController.swift-

import UIKit 

class InitialViewController: BaseViewController {

override func viewDidLoad() {
    super.viewDidLoad()

    // Gradient Layer
    view.addGradientBackground(colorTop: COLOR_ROYALRED2, colorBottom: COLOR_ROYALRED1)

    // Button
    let startButton = UIButton()
    startButton.createRectangleButton(buttonPositionX: 50, buttonPositionY: 20, buttonWidth: 200, buttonHeight: 50, buttonTilte: "START")
    self.view.addSubview(startButton)

    }
}

Answer 1

尝试这个：

extension UIButton {
   func createRectangleButton(buttonPositionX: Double, buttonPositionY: Double ,buttonWidth: Double, buttonHeight: Double, buttonTilte: String) {
       let button = self // changes made here
       button.frame = CGRect(x: buttonPositionX, y: buttonPositionY, width: buttonWidth, height: buttonHeight)
       button.setTitle(buttonTilte, for: .normal)
       button.backgroundColor = COLOR_WHITE
       button.tintColor = COLOR_BLACK
   }
}