import UIKit

class MainViewController: UITabBarController {

    //MARK:属性 懒加载

    lazy var composeBtn = UIButton(composeForeImageName: "tabbar_compose_icon_add", composeBackImageName: "tabbar_compose_button")

    //MARK:重写方法

    override func viewDidLoad() {

        super.viewDidLoad()

        tabBar.addSubview(composeBtn)

    }

    override func viewWillLayoutSubviews() {

        composeBtn.center = CGPoint(x: tabBar.center.x, y:tabBar.bounds.height * 0.5)

        //方法1：Selector("方法名")  Swift已经不推荐使用，会被提示改成第二种代替

//        composeBtn.addTarget(self, action:Selector(("composeBtnClick")), for: .touchUpInside)

        //方法2：Selector("类名.方法名") 推荐写法

        composeBtn.addTarget(self, action:#selector(MainViewController.composeBtnClick), for: .touchUpInside)

        //方法3："方法名"

//          composeBtn.addTarget(self, action:"composeBtnClick", for: .touchUpInside)

    }

}

//MARK:事件监听

extension MainViewController{

    //这里必须要加@objc 否则会崩溃

    @objc func composeBtnClick(){

        print("composeBtnClick")

    }

}