这里我尝试访问我的handleTap（）函数，它是我在另一个文件中创建的一个OBJ C函数，我需要它留在那个文件中，那么我如何从第二个ViewController访问这个函数呢？

import UIKit

class SecondViewController: UIViewController {
    
   
    var stackView = UIStackView()
    
    var circle: Button = {
        let button = Button()
        button.addTarget(self, action: #selector(handleTap), for: .touchUpInside)
        return button
    }()

这就是我在靠近底部的另一个文件中定义handleTap（）的方式。它是一个文件名Button.swift，也许可以在SecondViewController上做一个扩展，包括handleTap（），但我不知道如何做。

    import UIKit

class Button: UIButton {
    override init(frame: CGRect) {
        super.init(frame: frame)
        createCircle()
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    let percentageLabel: UILabel = {
        let label = UILabel()
        label.text = ""
        label.textAlignment = .center
        label.font = UIFont.boldSystemFont(ofSize: 28)
        label.textColor = UIColor(red: 0.59, green: 0.42, blue: 0.23, alpha: 1.00)
        return label
        
    }()
    let shapeLayer = CAShapeLayer()
    
    func createCircle() {
        
        let trackLayer = CAShapeLayer()
        
        let button = UIButton(type: .custom)
        button.frame = CGRect(x: 0, y: 0, width: 100, height: 100)
        button.layer.cornerRadius = 0.5 * button.bounds.size.width
        button.clipsToBounds = true
        button.center = center
        
        addSubview(button)
        
        let circularPath = UIBezierPath(arcCenter: .zero, radius: 50, startAngle: 0, endAngle: 2 * CGFloat.pi, clockwise: true)
        
        trackLayer.path = circularPath.cgPath
        
        trackLayer.strokeColor = UIColor(red: 0.82, green: 0.69, blue: 0.52, alpha: 1.00).cgColor
        trackLayer.fillColor = UIColor.clear.cgColor
        trackLayer.lineWidth = 10
        trackLayer.position = center
        layer.addSublayer(trackLayer)
        
        shapeLayer.path = circularPath.cgPath
        
        shapeLayer.strokeColor = UIColor(red: 0.59, green: 0.42, blue: 0.23, alpha: 1.00).cgColor
        shapeLayer.fillColor = UIColor.clear.cgColor
        shapeLayer.lineWidth = 10
        shapeLayer.lineCap = CAShapeLayerLineCap.round
        shapeLayer.position = center
        shapeLayer.transform = CATransform3DMakeRotation(-CGFloat.pi / 2, 0, 0, 1)
        
        addSubview(percentageLabel)
        
        percentageLabel.frame = CGRect(x: 0, y: 0, width: 150, height: 150)
        percentageLabel.center = center
        //  return CGPoint(x: positionX, y: positionY)
        
    }
    
    var done = 0
    var toDo = 0
    
    @objc func handleTap(sender: UIButton) {
        toDo = 5
        if done < toDo {
            done += 1
        } else {
            done -= toDo
        }
        let percentage = CGFloat(done) / CGFloat(toDo)
        percentageLabel.text = "\(Int(percentage * 100))%"
        
        DispatchQueue.main.async {
            self.shapeLayer.strokeEnd = percentage
        }
        layer.addSublayer(shapeLayer)
    }
}