–>MsgViewController<–

class MsgViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        self.view.backgroundColor = UIColor.orange
        
        let btn = UIButton(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
        self.view.addSubview(btn)
        btn.setTitle("Send Msg", for: .normal)
        btn.backgroundColor = UIColor.blue
        btn.addTarget(self, action: #selector(self.sendMsg), for: .touchDown)
        
        //constraints
        btn.translatesAutoresizingMaskIntoConstraints = false
        
        //method 1
        /*
        NSLayoutConstraint.activate([
            btn.centerXAnchor.constraint(equalTo: self.view.centerXAnchor),
            btn.centerYAnchor.constraint(equalTo: self.view.centerYAnchor),
            btn.widthAnchor.constraint(equalToConstant: btn.frame.width),
            btn.heightAnchor.constraint(equalToConstant: btn.frame.height)
        ])
        */
        
        //method 2
        btn.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true
        btn.centerYAnchor.constraint(equalTo: self.view.centerYAnchor).isActive = true
        btn.widthAnchor.constraint(equalToConstant: btn.frame.width).isActive = true
        btn.heightAnchor.constraint(equalToConstant: btn.frame.height).isActive = true
        
        
       
    }

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


    @objc func sendMsg(){
        if MFMessageComposeViewController.canSendText() {
            let c = MFMessageComposeViewController()
            c.body = "短信内容，欢迎来到jobyme88.com"
            c.recipients = ["15866668888"]
            c.messageComposeDelegate = self
            self.present(c, animated: true, completion: nil )
        } else {
            print("本设备不能发送短信")
        }
    }
}

extension MsgViewController: MFMessageComposeViewControllerDelegate{
    func messageComposeViewController(_ controller: MFMessageComposeViewController, didFinishWith result: MessageComposeResult) {
        switch result {
        case .sent:
            print("已发送")
        case .cancelled:
            print("用户取消")
        case .failed :
            print("发送失败")
        }
    }
    
    
}