对于密钥取消,此类不符合密钥值编码

Question

我一直收到这个错误: Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<FoodTracker.MealViewController 0x7faa9ed189d0> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key cancel.'

我正在尝试完成Apple开发人员指南以开始使用iOS应用程序.我的代码和故事板看起来与他们在示例文件中的完全一样.我希望新鲜的眼睛能够看到我不是的东西？

import UIKit
import os.log

class MealViewController: UIViewController, UITextFieldDelegate, UIImagePickerControllerDelegate, UINavigationControllerDelegate {

    //MARK: Properties
    @IBOutlet weak var nameTextField: UITextField!
    @IBOutlet weak var photoImageView: UIImageView!
    @IBOutlet weak var ratingControl: RatingControl!
    @IBOutlet weak var saveButton: UIBarButtonItem!
    /*
     This value is either passed by 'MealTableViewController' in
     'prepare(for:sender) or constructed as part of adding a new meal.
    */
    var meal: Meal?

    override func viewDidLoad() {
        super.viewDidLoad()

        // Handle the text field's user input through delegate callbacks
        nameTextField.delegate = self

        // Enable save button only if text field has valid Meal name
        updateSaveButtonState()
    }

    //MARK: UITextFieldDelegate
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        // Hide the keyboard
        textField.resignFirstResponder()
        return true
    }
    func textFieldDidEndEditing(_ textField: UITextField) {
        updateSaveButtonState()
        navigationItem.title = textField.text
    }
    func textFieldDidBeginEditing(_ textField: UITextField) {
        // Disable save button while editing
        saveButton.isEnabled = false
    }

    //MARK: UIImagePickerControllerDelegate
    func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
        // Dismiss the picker if the user canceled
        dismiss(animated: true, completion: nil)
    }
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
        // The info dictionary may contain multiple representations of the image. You want to use the original.
        guard let selectedImage = info[UIImagePickerControllerOriginalImage] as? UIImage else {
            fatalError("Expected a dictionary containing an image, but was provided the following: \(info)")
        }
        // Set photoImageView to display the selected image
        photoImageView.image = selectedImage
        // Dismiss the picker
        dismiss(animated: true, completion: nil)
    }

    //MARK: Navigation
    @IBAction func cancel(_ sender: UIBarButtonItem) {
        dismiss(animated: true, completion: nil)
    }


    // Configure view controller before it's presented
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        super.prepare(for: segue, sender: sender)

        // Configure destination view controller only when save button pressed
        guard let button = sender as? UIBarButtonItem, button === saveButton else {
            os_log("The save button was not pressed, cancelling", log: OSLog.default, type: .debug)
            return
        }

        let name = nameTextField.text ?? ""
        let photo = photoImageView.image
        let rating = ratingControl.rating

        // Set meal to be passed to MealTableViewController after unwind segue
        meal = Meal(name: name, photo: photo, rating: rating)
    }

    //MARK: Actions
    @IBAction func selectImageFromPhotoLibrary(_ sender: UITapGestureRecognizer) {
        // Hide the keyboard
        nameTextField.resignFirstResponder()
        // UIImagePickerController is a view controller that lets a user pick media from their photo library
        let imagePickerController = UIImagePickerController()
        // Only allow photos to be picked, not taken
        imagePickerController.sourceType = .photoLibrary
        // Make sure ViewController is notified when the user picks an image
        imagePickerController.delegate = self
        present(imagePickerController, animated: true, completion: nil)
    }

    //MARK: Private Methods
    private func updateSaveButtonState() {
        // Disable the save button if the text field is empty
        let text = nameTextField.text ?? ""
        saveButton.isEnabled = !text.isEmpty
    }
}

还有一些其他文件,但请让我知道你需要什么,因为我对Swift/XCode很新,不知道提供什么/不提供什么.

Answer 1

这意味着您的故事板上有一些连接到IBOutlet的故事板,cancel但您的班级中没有此IBOutlet.所以编译器cancel在你的类中找不到Key (它意味着属性).您应该在故事板中找到该按钮(我认为它是UIButton,因为名称),单击鼠标右键并单击"x"删除该连接.或者您可能想要删除此按钮.或者您可能希望将此IBOutlet添加到您的班级.

Answer 2

我同意Alex Shubin在他的回答中提到的一个可操作的解决方案,比如"寻找任何不存在的连接并删除它们".我遇到了同样的问题,他的建议修复了这个错误.对于那些刚接触编程的人和像我这样的Xcode,有关如何在故事板中找到x按钮的更多信息可能会有所帮助.

单击故事板中视图控制器顶部的黄色圆圈.

然后在实用程序栏的右上角显示连接检查器.连接检查器是最右侧的菜单,带有右箭头的圆圈.单击它,您应该看到该视图控制器的所有连接.

我在我的应用程序中包含了一个屏幕截图.

Answer 3

在“身份检查器”下检查模块名称。必须选择模块名称，或者必须检查“从目标继承模块”。如果有多个模块，请选择适当的模块。