ios - 委托(delegate)仍然为零

Question

我将用户数据从名为 CreateNewAccount 的 View Controller 传递到另一个名为 ThanksForJoining 的 View Controller 。出于某种原因，我的委托(delegate)是 nil。我正在使用 segue 以将我的 vc.delegate 设置为 self (= self) 并且 segue 标识符“thanksForJoining”指的是将 CreateNewAccount 连接到 Storyboard 上的 ThanksForJoining 的 segue。但不知何故，委托(delegate)仍然是 nil。

创建新帐户:

import UIKit

protocol UserInfoDelegate {
   func sendUserInfo(firstName: String, lastName: String, username: String, password: String)
}

class CreateNewAccount: UIViewController{
    @IBOutlet weak var FNInput: UITextField!
    @IBOutlet weak var LNInput: UITextField!
    @IBOutlet weak var usernameInput: UITextField!
    @IBOutlet weak var passwordInput: UITextField!

    var infoDelegate: UserInfoDelegate?

    @IBAction func sendInfo(_ sender: Any) {
        if(infoDelegate != nil){
            if(FNInput.text != nil && LNInput.text != nil && usernameInput.text != nil && passwordInput.text != nil){
                let firstName = FNInput.text
                let lastName = LNInput.text
                let username = usernameInput.text
                let password = passwordInput.text

                infoDelegate?.sendUserInfo(firstName: firstName!, lastName: lastName!, username: username!, password: password!)
            }
        }
    }
}

感谢加入:

import UIKit

class ThanksForJoining: UIViewController, UserInfoDelegate {
    @IBOutlet weak var fName: UILabel!

    func sendUserInfo(firstName: String, lastName: String, username: String, password: String) {
        print(firstName)
        fName.text = firstName
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if (segue.identifier == "thanksForJoining") {
            let createNewAccount: CreateNewAccount = segue.destination as! CreateNewAccount
            createNewAccount.infoDelegate = self
        }
    }
}

Answer 1

首先，您需要确认:

• 您通过 segue 将 CreateNewAccount 连接到 ThanksForJoining。

• segue 的标识符设置为 thanksForJoining 正确(注意字母大小写。)

如果两者中有任何一个不成立，你就浪费了一点时间，我就浪费了准备大台风的时间。更新您的问题以澄清正在发生的事情并等待有人帮助您...

---

假设以上两件事，prepare(for:sender:) 在源 View Controller 上被调用。您需要在 CreateNewAccount 类中实现它。

创建新帐户:

import UIKit

class CreateNewAccount: UIViewController {
    @IBOutlet weak var firstNameInput: UITextField!
    @IBOutlet weak var lastNameInput: UITextField!
    @IBOutlet weak var usernameInput: UITextField!
    @IBOutlet weak var passwordInput: UITextField!

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "thanksForJoining" {
            let destinationVC = segue.destination as! ThanksForJoining
            if
                let firstName = firstNameInput.text, !firstName.isEmpty,
                let lastName = lastNameInput.text, !lastName.isEmpty,
                let username = usernameInput.text, !username.isEmpty,
                let password = passwordInput.text, !password.isEmpty
            {
                destinationVC.receiveUserInfo(firstName: firstName, lastName: lastName, username: username, password: password)
            }
        }
    }
}

感谢加入:

import UIKit

class ThanksForJoining: UIViewController {
    var firstName: String?

    @IBOutlet weak var firstNameLabel: UILabel!

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        firstNameLabel.text = firstName
    }

    func receiveUserInfo(firstName: String, lastName: String, username: String, password: String) {
        print(firstName)
        self.firstName = firstName
    }
}

似乎委托(delegate)模式对您的目的来说有点太多了，您只需要在目标 View Controller ThanksForJoining 中定义一个数据传递方法。

我假设您已经通过 CreateNewAccount 的某个按钮连接了您的 segue。如果 segue 是从 View Controller (而不是按钮)连接的，则上面的代码需要稍作修改。

但是无论如何，在您的原始代码中，永远不会调用 ThanksForJoining 中的方法 prepare(for:sender:)，因此永远不会设置委托(delegate)。因此，委托(delegate)仍然是 nil。