Swift:使用委托将数据发送到另一个视图控制器

protocol DataDelegate: AnyObject {
    func didSendData(data: String)
}

import UIKit

class ViewControllerA: UIViewController {
    weak var dataDelegate: DataDelegate?

    @IBOutlet weak var textField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()
        // 设置代理
        textField.delegate = self
    }

    @IBAction func sendDataButtonTapped(_ sender: UIButton) {
        guard let text = textField.text else { return }
        dataDelegate?.didSendData(data: text)
        navigationController?.pushViewController(ViewControllerB(), animated: true)
    }
}

extension ViewControllerA: UITextFieldDelegate {
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        return true
    }
}

import UIKit

class ViewControllerB: UIViewController, DataDelegate {
    @IBOutlet weak var label: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        // 设置代理
        let viewControllerA = ViewControllerA()
        viewControllerA.dataDelegate = self
    }

    func didSendData(data: String) {
        label.text = data
    }
}

weak var dataDelegate: DataDelegate?

let viewControllerA = ViewControllerA()
viewControllerA.dataDelegate = self