swift 学习之hello窗口弹出

import UIKit

class ViewController: UIViewController {
    @IBAction func touch(_ sender: UIButton) {
        print("halo")
        let ac = UIAlertController(title: "message", message: "Do U Love Me", preferredStyle: .alert)
        let btn = UIAlertAction(title: "Yes,I do", style: .default, handler: nil)
        ac.addAction(btn)
        self .present(ac, animated: true, completion: nil)
        
        
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}