Swift – 點擊 button alert

於 “ViewController.swift” 加入以下

@IBAction func showMessage(sender: UIButton){
        let alertController = UIAlertController(title:"My first app", message:"Testing", preferredStyle: UIAlertController.Style.alert)
        
        alertController.addAction(UIAlertAction(title:"OK",style:UIAlertAction.Style.default, handler: nil))
        
        present(alertController, animated: true,completion: nil)
}

於 “Main.storyboard” ，點擊 你的button, 按住 “control” 後拖動到 “ViewController”, 然後再選擇function名稱（這裡的範例是 “showMessage”) 如下圖