Ios 在UITabBarController中声明代理时，在两个ViewController之间传递数据时出错

我尝试在两个ViewController之间传递数据，初始调用由UITabBarController进行

这就是我正在做的。我正在使用一个名为RaisedTabBarController的类向TabBarController添加一个自定义按钮，它可以很好地显示按钮，我的问题是，当我点击“自定义”按钮时，我希望它将我带到FirstViewController，然后我希望通过协议将数据从FirstViewController传递到SecondViewController，但由于某种原因，我得到了一个错误，在我看来没有任何意义，它抱怨在SecondViewController中无法访问标签

以下是错误：

致命错误：在展开可选值时意外发现nil

这是代码

来自GitHub的类引用： 塔巴控制器 在这里，我添加了自定义按钮并调用FirstViewController

import UIKit
/// TabBarController subclasses RaisedTabBarController
class TabBarController: RaisedTabBarController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // Insert empty tab item at center index. In this case we have 5 tabs.
        self.insertEmptyTabItem("", atIndex: 2)
        // Raise the center button with image
        let img = UIImage(named: “myImage”)
        self.addRaisedButton(img, highlightImage: nil, offset: -10.0)
    }
    // Handler for raised button
    override func onRaisedButton(_ sender: UIButton!) {
        super.onRaisedButton(sender)
        // Go to FirstViewController
        let pvc = storyboard?.instantiateViewController(withIdentifier: “firstStoryBoardID”) as! FirstViewController
        /// Here, I’m not sure if this is the right way to tell that 
        /// SecondViewController will be the delegate not TabBarController, seem to work
        pvc.delegate = SecondViewController() as FirstViewControllerDelegate
        self.present(pvc, animated:true, completion:nil)
    }
}

protocol FirstViewControllerDelegate {
    func messageData(greeting: String)
}

class FirstViewController: UIViewController{
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    func sendData() {
        self.delegate?.messageData(greeting: “Hello SecondViewController”)
    }
}

class SecondViewController: UIViewController, FirstViewControllerDelegate{

    @IBOutlet weak var labelMessage: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
    }
    func messageData(greeting: String) {
        /// I do get message from FirstViewController
        print(" Message received from FirstViewController: \(greeting)")

        /// Here I get error, fatal error: unexpectedly found nil while unwrapping an Optional value
        ///  I think it has something to do with the labelMessage not being accessible, but why? 
        labelMessage.text = greeting
    }
}

pvc.delegate = svc

FirstViewController 我想从这里向SecondViewController发送数据

import UIKit
/// TabBarController subclasses RaisedTabBarController
class TabBarController: RaisedTabBarController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // Insert empty tab item at center index. In this case we have 5 tabs.
        self.insertEmptyTabItem("", atIndex: 2)
        // Raise the center button with image
        let img = UIImage(named: “myImage”)
        self.addRaisedButton(img, highlightImage: nil, offset: -10.0)
    }
    // Handler for raised button
    override func onRaisedButton(_ sender: UIButton!) {
        super.onRaisedButton(sender)
        // Go to FirstViewController
        let pvc = storyboard?.instantiateViewController(withIdentifier: “firstStoryBoardID”) as! FirstViewController
        /// Here, I’m not sure if this is the right way to tell that 
        /// SecondViewController will be the delegate not TabBarController, seem to work
        pvc.delegate = SecondViewController() as FirstViewControllerDelegate
        self.present(pvc, animated:true, completion:nil)
    }
}

protocol FirstViewControllerDelegate {
    func messageData(greeting: String)
}

class FirstViewController: UIViewController{
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    func sendData() {
        self.delegate?.messageData(greeting: “Hello SecondViewController”)
    }
}

class SecondViewController: UIViewController, FirstViewControllerDelegate{

    @IBOutlet weak var labelMessage: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
    }
    func messageData(greeting: String) {
        /// I do get message from FirstViewController
        print(" Message received from FirstViewController: \(greeting)")

        /// Here I get error, fatal error: unexpectedly found nil while unwrapping an Optional value
        ///  I think it has something to do with the labelMessage not being accessible, but why? 
        labelMessage.text = greeting
    }
}

pvc.delegate = svc

第二视图控制器 这里我想接收从FirstViewController发送的数据

import UIKit
/// TabBarController subclasses RaisedTabBarController
class TabBarController: RaisedTabBarController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // Insert empty tab item at center index. In this case we have 5 tabs.
        self.insertEmptyTabItem("", atIndex: 2)
        // Raise the center button with image
        let img = UIImage(named: “myImage”)
        self.addRaisedButton(img, highlightImage: nil, offset: -10.0)
    }
    // Handler for raised button
    override func onRaisedButton(_ sender: UIButton!) {
        super.onRaisedButton(sender)
        // Go to FirstViewController
        let pvc = storyboard?.instantiateViewController(withIdentifier: “firstStoryBoardID”) as! FirstViewController
        /// Here, I’m not sure if this is the right way to tell that 
        /// SecondViewController will be the delegate not TabBarController, seem to work
        pvc.delegate = SecondViewController() as FirstViewControllerDelegate
        self.present(pvc, animated:true, completion:nil)
    }
}

protocol FirstViewControllerDelegate {
    func messageData(greeting: String)
}

class FirstViewController: UIViewController{
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    func sendData() {
        self.delegate?.messageData(greeting: “Hello SecondViewController”)
    }
}

class SecondViewController: UIViewController, FirstViewControllerDelegate{

    @IBOutlet weak var labelMessage: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
    }
    func messageData(greeting: String) {
        /// I do get message from FirstViewController
        print(" Message received from FirstViewController: \(greeting)")

        /// Here I get error, fatal error: unexpectedly found nil while unwrapping an Optional value
        ///  I think it has something to do with the labelMessage not being accessible, but why? 
        labelMessage.text = greeting
    }
}

pvc.delegate = svc

知道为什么在SecondViewController中出现错误吗？如果标签在SecondViewController中声明，为什么标签不可访问？ 理想情况下，我希望能够调用方法onRaisedButton\uSender:UIButton！直接从SecondViewController，但无需子类RaisedTabBarController。我不知道这是否能解决错误，但我认为这会使我的代码更干净

编辑：2017年6月19日-已解决 我想要的效果可以直接在XCode中，在故事板中实现。我停止使用第三方类RaisedTabBarController，问题解决了。

这似乎是错误的

pvc.delegate = SecondViewController() as FirstViewControllerDelegate

尝试实例化第二个ViewController，就像在故事板中对第一个进行实例化一样

let svc = storyboard?.instantiateViewController(withIdentifier: “secondStoryBoardID”) as! SecondViewController

然后将代理设置为SecondViewController

import UIKit
/// TabBarController subclasses RaisedTabBarController
class TabBarController: RaisedTabBarController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // Insert empty tab item at center index. In this case we have 5 tabs.
        self.insertEmptyTabItem("", atIndex: 2)
        // Raise the center button with image
        let img = UIImage(named: “myImage”)
        self.addRaisedButton(img, highlightImage: nil, offset: -10.0)
    }
    // Handler for raised button
    override func onRaisedButton(_ sender: UIButton!) {
        super.onRaisedButton(sender)
        // Go to FirstViewController
        let pvc = storyboard?.instantiateViewController(withIdentifier: “firstStoryBoardID”) as! FirstViewController
        /// Here, I’m not sure if this is the right way to tell that 
        /// SecondViewController will be the delegate not TabBarController, seem to work
        pvc.delegate = SecondViewController() as FirstViewControllerDelegate
        self.present(pvc, animated:true, completion:nil)
    }
}

protocol FirstViewControllerDelegate {
    func messageData(greeting: String)
}

class FirstViewController: UIViewController{
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    func sendData() {
        self.delegate?.messageData(greeting: “Hello SecondViewController”)
    }
}

class SecondViewController: UIViewController, FirstViewControllerDelegate{

    @IBOutlet weak var labelMessage: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
    }
    func messageData(greeting: String) {
        /// I do get message from FirstViewController
        print(" Message received from FirstViewController: \(greeting)")

        /// Here I get error, fatal error: unexpectedly found nil while unwrapping an Optional value
        ///  I think it has something to do with the labelMessage not being accessible, but why? 
        labelMessage.text = greeting
    }
}

pvc.delegate = svc

---

你们初始化了第二视图控制器吗？我不确定我应该在哪里初始化它。仅供参考-如果协议调用直接从FirstViewController进行，则在FirstViewController和SecondViewController之间传递数据有效。确保SecondViewController符合协议。好的，从TabBarController我想转到FirstVC而不是SecondVC。仅供参考-我正在从FirstVC获取我在SecondVC中期望的数据，我只是得到一个关于标签为零的错误。您可以尝试检查插座是否在故事板中正确连接。否则，在视图中将出现一个断点方法，并查看您设置的其他插座是否为零，如果所有插座均为零或self为零，则您必须从故事板实例化控制器，如我所述。