控制器之间的委派不起作用。为什么？

Question

我尝试使用委托将数据从 Detail2( ViewController( 中的textField发送到ViewController中的数组。我在这里使用了打印方法，第一次打印显示一个元素已添加到数组中，但低于ViewVillAppear()的第二个打印方法显示数组为空。如何？我希望能够使用委托将数据添加到我的表中。

["sdsd"] 首次从控制台打印 [] 从控制台进行第二次打印

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
@IBOutlet var add: UIBarButtonItem!
@IBOutlet var tv: UITableView!
var array :[String] = []
override func viewDidLoad() {
    super.viewDidLoad()
    tv.register(UITableViewCell.self, forCellReuseIdentifier: "cell") 
}
override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "segue" {
        let vc: Detail2 = segue.destination as! Detail2
        vc.delegate = self
    }
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return array.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
    cell.textLabel?.text = array[indexPath.row]
    return cell
}
func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
    if editingStyle == .delete {
        array.remove(at: indexPath.row )
        tv.reloadData()
    }
}
func alert () {
}

 override func viewWillAppear(_ animated: Bool) {
        tv.reloadData()
        print(array)
    }
}
extension ViewController: Data {
    func tekst(data: String) {
        array.append(data)
        print(array)
    }   
}

和细节2

    protocol Data {
    func tekst (data: String)
}
class Detail2: UIViewController {
    var delegate: Data? = nil
    @IBAction func btn(_ sender: Any) {
        let sb  = storyboard?.instantiateViewController(withIdentifier: "Main" ) as! ViewController
        navigationController?.pushViewController(sb, animated: true)
        if delegate != nil {
            if txtfield.text != nil {
                let napis = txtfield.text
                delegate?.tekst(data: napis!)   
            }   
        }   
    }
    @IBOutlet var btn: UIButton!
    @IBOutlet var txtfield: UITextField!
    override func viewDidLoad() {
        super.viewDidLoad()
        btn.backgroundColor = UIColor.blue
        btn.tintColor = UIColor.white
        btn.layer.cornerRadius = 25
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

Answer 1

只需通过以下方式更新您的函数：

@IBAction func btn(_ sender: Any) {
        if delegate != nil {
        if txtfield.text != nil {
            let napis = txtfield.text
            delegate?.tekst(data: napis!)
        }
    navigationController?.popViewController(animated: true)
    }
}

更新：

extension ViewController: Data {
    func tekst(data: String) {
        array.append(data)
        print(array)
        self.tv.reloadData()
    }   
}

Answer 2

你需要在

完成处理程序中添加这个delegate?.tekst(data: napis!)，因为你使用的是navigationController，所以没有完成处理程序的选项，所以不得不像这样添加UINavigationController扩展：

extension UINavigationController {
    public func pushViewController(viewController: UIViewController,
                                   animated: Bool,
                                   completion:  (() -> Void)?) {
        CATransaction.begin()
        CATransaction.setCompletionBlock(completion)
        pushViewController(viewController, animated: animated)
        CATransaction.commit()
    }
}

更改此内容

navigationController?.pushViewController(sb, animated: true){
    if delegate != nil {
        if txtfield.text != nil {
            let napis = txtfield.text
            delegate?.tekst(data: napis!)
        }

Answer 3

在 Detail2 视图中更新代码

@IBAction func btn(_ sender: Any) {
       if delegate != nil {
           if txtfield.text != nil {
             let napis = txtfield.text
             delegate?.tekst(data: napis!)
            }
        }
        navigationController?.popViewController(animated: true)
}

Answer 4

在ViewController中实现委托方法

 func tekst (data: String) { 
    array.append(data)
 }

//详细地

@IBAction func btn(_ sender: Any) {
    if txtfield.text != nil {
        let napis = txtfield.text
        delegate?.tekst(data: napis!)
    }
     /// dismiss detail here  don't push main again
     self.navigationController?.popViewController(animated: true)
}