最简单使用

let btn = UIButton.init {
            // 按钮点击事件
        }
        // 可以进行其他按钮设置

使用按钮

override func viewDidLoad() {
    super.viewDidLoad()
    let btn = UIButton.init(setImage: "首页未选中", frame: CGRect.init(x:100, y: 100, width: 100, height: 100)) {
            // 点击的回调
            print("btn")
        }
    view.addSubview(btn)
}

实现原理(可以根据需要自行扩展)

import UIKit

typealias buttonClick = (()->()) // 定义数据类型(其实就是设置别名)
extension UIButton{
    // 改进写法【推荐】
    private struct RuntimeKey {
        static let actionBlock = UnsafeRawPointer.init(bitPattern: "actionBlock".hashValue)
        /// ...其他Key声明
    }
    /// 运行时关联
    private var actionBlock: buttonClick? {
        set {
            objc_setAssociatedObject(self, UIButton.RuntimeKey.actionBlock!, newValue, .OBJC_ASSOCIATION_COPY_NONATOMIC)
        }
        get {
            return  objc_getAssociatedObject(self, UIButton.RuntimeKey.actionBlock!) as? buttonClick
        }
    }
     /// 点击回调
    @objc func tapped(button:UIButton){
        if self.actionBlock != nil {
            self.actionBlock!()
        }
    }
    /// 快速创建
    convenience init(action:@escaping buttonClick){
        self.init()
        self.addTarget(self, action:#selector(tapped(button:)) , for:.touchUpInside)
        self.actionBlock = action
        self.sizeToFit()
    }
    /// 快速创建
    convenience init(setImage:String, action:@escaping buttonClick){
        self.init()
        self.frame = frame
        self.setImage(UIImage(named:setImage), for: UIControlState.normal)
        self.addTarget(self, action:#selector(tapped(button:)) , for:.touchUpInside)
        self.actionBlock = action
        self.sizeToFit()
    }
    /// 快速创建按钮 setImage: 图片名 frame:frame action:点击事件的回调
    convenience init(setImage:String, frame:CGRect, action: @escaping buttonClick){
        self.init( setImage: setImage, action: action)
        self.frame = frame
    }
 
}