将数据从SearchBar传递到UILabel

Question

如何将数据从搜索栏传递到其他视图控制器中的UILabel

Passing Data between View Controllers我已经在堆栈上尝试了多个问题，但是它不起作用，或者模拟器最终对我崩溃了

class FirstVC: UIViewController, DataEnteredDelegate {

    @IBOutlet weak var label: UILabel!

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "showSecondViewController" {
            let secondViewController = segue.destination as! SecondVC
            secondViewController.delegate = self
        }
    }

    func userDidEnterInformation(info: String) {
        label.text = info
    }
}



 // protocol used for sending data back

protocol DataEnteredDelegate: class {
    func userDidEnterInformation(info: String)
}

class SecondVC: UIViewController {

    // making this a weak variable so that it won't create a strong reference cycle
    weak var delegate: DataEnteredDelegate? = nil

    @IBOutlet weak var searchBar: UISearchBar!

    @IBAction func sendTextBackButton(sender: AnyObject) {

        // call this method on whichever class implements our delegate protocol
        delegate?.userDidEnterInformation(info: searchBar.text!)

        // go back to the previous view controller
        _ = self.navigationController?.popViewController(animated: true)
    }
}

Answer 1

我在您的代码中没有发现任何可疑的内容，这些可导致应用程序崩溃。同时，对于视图控制器之间的数据传输，我们可以使用委托和NotificationCenter。下面的代码使用NotificationCenter

let kStringTransfer = "StringTransferNotification"

class FirstViewController: UIViewController, DataEnteredDelegate {

    @IBOutlet weak var textField: UITextField!
    override func viewDidLoad() {
        super.viewDidLoad()
        NotificationCenter.default.addObserver(self, selector: #selector(setString(notify:)), name: NSNotification.Name(rawValue: kStringTransfer), object: nil)
    }

    func getSecondVC() {
        if let second = self.storyboard?.instantiateViewController(withIdentifier: "Second") as? ViewController {
            self.navigationController?.pushViewController(second, animated: true)
        }
    }

    @IBAction func searchBarBtn(_ sender: Any) {
        //go to search view controller
        getSecondVC()
    }

    @objc func setString(notify: Notification) {
        //set search bar string to text field
        textField.text = notify.object as? String
    }

}

class SecondViewController: UIViewController, UISearchBarDelegate {

    @IBOutlet weak var searchBar: UISearchBar!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        searchBar.delegate = self
    }

    @IBAction func goBackBtn(_ sender: Any) {
        NotificationCenter.default.post(name: NSNotification.Name(rawValue: kStringTransfer), object: searchBar.text)
        self.navigationController?.popViewController(animated: true)
    }
}

Answer 2

[当我需要在两个viewController之间传递很小的值时，我不使用委托，只需在第二个视图中创建一个变量并像这样传递。

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if (segue.identifier == "showView") {
        let vc = segue.destination as! secondViewController
        vc.stringTemp = "My string"
    }
}