Extension UIButton

UIButton+extension.swift

extension UIButton {
    convenience init(title: String,
                     backgroundColor: UIColor, 
                     font: UIFont?,
                     isShadow: Bool,
                     cornerRadius: CGFloat
                     titleColor: UIColor) {
       
      self.init(type: .system) //инициализатор через type
      
      //входные встроенные функции:
      self.setTitle(title, for: .normal)
      self.setTitleColor(titleColor, for: .normal)
      self.backgroundColor = backgroundColor
      self.titleLabel?.font = font
      
      self.layer.cornerRadius = cornerRadius
      
      if isShadow {
      self.layer.cornerRadius = UIColor.black.cgColor
      self.layer.shadowradius = 4
      self.layer.shadowOpacity = 0.2
      self.layer.shadowOpacity = CGSize(width: 0, height: 4)
      }
      
    }

ViewController.swift

import UIKit

class ViewController: UIViewController {
 let emailButton = UIButton(title: "Email", titleColor: .black .....) 
  let loginButton = UIButton(title: "Email", titleColor: .black .....) 
}