ios - 有人可以看到我在尝试使用 coreData 保存事件时缺少什么吗？

Question

我正在构建一个简单的应用程序，我可以在其中将餐食(食物)添加到列表中，然后使用另一个 VC 的 UIPicker 选取这些餐食。这很好用，但我也无法保存它。 (重新启动后不会保存任何数据)。我正在尝试使用 coreData 执行此操作，我可以在代码列表中看到事件/更改实际上正在保存和加载。 (我已经在其他应用程序中成功使用了coreData)

有人可以帮助我吗？我应该怎么办？我对 IOS 开发和 Swift 还很陌生，所以请说得清楚具体 =)

这是我的代码:

如果您还需要任何其他帮助，请告诉我。非常感谢 StackOverflow!

VC 1:

import UIKit
import CoreData


var List = ["Pasta Pesto", "Spenat Soppa", "Ris, Quorn & Currysås", "Lins Soppa"]


class ViewController: UIViewController {

@IBOutlet weak var monday: UITextField!
@IBOutlet weak var tuesday: UITextField!
@IBOutlet weak var wednesday: UITextField!
@IBOutlet weak var thursday: UITextField!
@IBOutlet weak var friday: UITextField!
@IBOutlet weak var saturday: UITextField!
@IBOutlet weak var sunday: UITextField!

var daysArray = [UITextField]()

let pickerView = ToolbarPickerView()

var selectedMenu : String?

override func viewDidLoad() {
    super.viewDidLoad()

    setupDelegateForPickerView()
    setupDelegatesForTextFields()
    coredataClass.loadData()
}




func setupDelegatesForTextFields() {
    //appending textfields in an array
    daysArray += [monday, tuesday, wednesday, thursday, friday, saturday, sunday]
    //using the array to set up the delegates, inputview for pickerview and also the             inputAccessoryView for the toolbar
    for day in daysArray {
        day.delegate = self
        day.inputView = pickerView
        day.inputAccessoryView = pickerView.toolbar
    }
}

func setupDelegateForPickerView() {
    pickerView.dataSource = self
    pickerView.delegate = self
    pickerView.toolbarDelegate = self
}
}

// Create an extension for textfield delegate

extension ViewController : UITextFieldDelegate {
func textFieldDidBeginEditing(_ textField: UITextField) {
    self.pickerView.reloadAllComponents()
}
}

// Extension for pickerview and toolbar

extension ViewController : UIPickerViewDelegate, UIPickerViewDataSource {
func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return List.count
}

func numberOfComponents(in pickerView: UIPickerView) -> Int {
    return 1
}

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component:     Int) -> String? {
    return List[row]

}


func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    // Check if the textfield isFirstResponder.
    if monday.isFirstResponder {
        monday.text = List[row]
    } else if tuesday.isFirstResponder {
        tuesday.text = List[row]
    } else if wednesday.isFirstResponder {
        wednesday.text = List[row]
    } else if thursday.isFirstResponder {
        thursday.text = List[row]
    } else if friday.isFirstResponder {
        friday.text = List[row]
    } else if saturday.isFirstResponder {
        saturday.text = List[row]
    } else if sunday.isFirstResponder {
        sunday.text = List[row]
    } else {
        //log errors
    }
}

//    PickerView's didSelectRow function can be simplified by changing it to below
//    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
//
//        for day in daysArray {
//            if day.isFirstResponder {
//                day.text = self.Menu[row]
//            }
//        }
//    }

}

extension ViewController: ToolbarPickerViewDelegate {

func didTapDone() {
    //      let row = self.pickerView.selectedRow(inComponent: 0)
    //      self.pickerView.selectRow(row, inComponent: 0, animated: false)
    //      selectedMenu = self.Menu[row]
    self.view.endEditing(true)
}

func didTapCancel() {
    self.view.endEditing(true)
}
}

VC 2:

import UIKit
import CoreData

class addViewController: UIViewController, UITextFieldDelegate {

@IBOutlet weak var input: UITextField!
@IBAction func addToMenu(_ sender: Any) {
    if (input.text != "")
    {
    List.append(input.text!)
    input.text = ""
    }

    input.delegate = self
    coredataClass.saveItems()
}



override func viewDidLoad() {
    super.viewDidLoad()

}

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    self.view.endEditing(true)
}

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

}

VC 3:

import UIKit
import CoreData



class tableViewController: UIViewController, UITableViewDelegate, UITableViewDataSource{
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return (List.count)

}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = UITableViewCell(style: .default, reuseIdentifier: "cell")
    cell.textLabel?.text = List[indexPath.row]
    cell.textLabel?.textColor = UIColor.white
    cell.backgroundColor = UIColor.clear




    return(cell)

}

func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle,     forRowAt indexPath: IndexPath) {
    if editingStyle == UITableViewCell.EditingStyle.delete
    {
        List.remove(at: indexPath.row)
        myTableView.reloadData()
    }

}





@IBOutlet weak var myTableView: UITableView!

override func viewDidAppear(_ animated: Bool) {
    myTableView.reloadData()
}

override func viewDidLoad() {
    super.viewDidLoad()
    coredataClass.saveItems()
    coredataClass.loadData()
}

}

应用程序委托(delegate):

import UIKit
import CoreData

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

var window: UIWindow?


func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    // Override point for customization after application launch.
    return true
}

func applicationWillResignActive(_ application: UIApplication) {
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
    // Use this method to pause ongoing tasks, disable timers, and invalidate graphics rendering callbacks. Games should use this method to pause the game.
}

func applicationDidEnterBackground(_ application: UIApplication) {
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

func applicationWillEnterForeground(_ application: UIApplication) {
    // Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.
}

func applicationDidBecomeActive(_ application: UIApplication) {
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

func applicationWillTerminate(_ application: UIApplication) {
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
}

 // MARK: - Core Data stack

    lazy var persistentContainer: NSPersistentContainer = {
        /*
         The persistent container for the application. This implementation
         creates and returns a container, having loaded the store for the
         application to it. This property is optional since there are legitimate
         error conditions that could cause the creation of the store to fail.
        */
        let container = NSPersistentContainer(name: "bonAPPetit")
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

                /*
                 Typical reasons for an error here include:
                 * The parent directory does not exist, cannot be created, or disallows writing.
                 * The persistent store is not accessible, due to permissions or data protection when the device is locked.
                 * The device is out of space.
                 * The store could not be migrated to the current model version.
                 Check the error message to determine what the actual problem was.
                 */
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        })
        return container
    }()

    // MARK: - Core Data Saving support

    func saveContext () {
        let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
                let nserror = error as NSError
                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
            }
        }
    }

}

核心数据类:

import UIKit
import CoreData

class coredataClass {

static var items = [MealsMenu]()

static let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext


    static func saveItems(){

           do{
            try coredataClass.context.save()
               print("SAVED")
           }catch{
           print("Error saving context with")
           }

       }


    static func loadData(){
           let request: NSFetchRequest<MealsMenu> = MealsMenu.fetchRequest()

           do{
            items = try coredataClass.context.fetch(request)
            print("LOADED")
           }catch{
               print("Error fetching data from context")
           }

       }
}

Answer 1

coreData 类中的 loadData 方法在获取成功后不会返回项目，因此要么从该方法返回，要么在获取成功后使用闭包

 static func loadData()->[MealsMenu]{
           let request: NSFetchRequest<MealsMenu> = MealsMenu.fetchRequest()

           do{
            items = try coredataClass.context.fetch(request)
            return items
            print("LOADED")
           }catch{
               print("Error fetching data from context")
            return items
           }

       }

并从 View Controller 使用返回的值来填充 TableView 数组