ios - 此类对于键取消不符合键值编码

Question

我不断收到此错误: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 Storyboard 看起来与示例文件中的代码和 Storyboard 完全一样。我希望新人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，但请告诉我您需要什么，因为我是 Swift/XCode 的新手，不确定该提供/不提供什么。

Answer 1

这意味着您的 Storyboard上有一些东西连接到 IBOutlet 称为 cancel 但您的类中没有这个 IBOutlet。因此编译器无法在您的类中找到 Key cancel(它表示属性)。你应该在 Storyboard 中找到那个按钮(我认为它是一个 UIButton 因为名字)，在它上面单击鼠标右键并单击“x”删除该连接。或者您可能想要完全删除此按钮。或者您可能想将此 IBOutlet 添加到您的类(class)中。