ios - CoreData 信息未显示在表格单元格中

Question

我有一个自定义单元格，并且使用核心数据，该单元格未更新。首先，我使用 Manual/None Codegen 选项在 .xcdatamodeId 处创建了一些实体。该项目无法构建，并且会给出以下错误:

“‘DreamLister.Item’类的 NSManagedObject 必须具有有效的 NSEntityDescription。”

在我为模型生成的类文件并删除所有 @objc(Item) 行后，项目已构建，但模拟器的单元格中不会出现任何内容。自定义单元格具有在 cellForRowAt 函数的代码中使用的标识符，我也在生成测试数据并像这样访问 AppDelegate

let ad = UIApplication.shared.delegate as! AppDelegate
let context = ad.persistentContainer.viewContext

编辑:在建议将 codegen 选项更改为类定义的答案之后，构建失败并出现 Swift 编译错误:命令:/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swiftc 失败，退出代码 1

这是我的 Controller 的代码

import UIKit
import CoreData

class MainVC: UIViewController, UITableViewDelegate, UITableViewDataSource, NSFetchedResultsControllerDelegate {

    @IBOutlet weak var tableView: UITableView!
    @IBOutlet weak var segment: UISegmentedControl!
    
    var controller: NSFetchedResultsController<Item>!
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        tableView.delegate = self
        tableView.dataSource = self
        
        generateTestData()
        attemptFetch()
       
        
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        
        let cell = tableView.dequeueReusableCell(withIdentifier: "ItemCell", for: indexPath) as! ItemCell
        
        configureCell(cell: cell, indexPath: indexPath as NSIndexPath)
        
        return cell
        
    }
    
    func configureCell(cell: ItemCell, indexPath: NSIndexPath) {
        
        let item = controller.object(at: indexPath as IndexPath)
        cell.configureCell(item: item)
        
    }
    
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        
        if let objs = controller.fetchedObjects , objs.count > 0 {
            
            let item = objs[indexPath.row]
            performSegue(withIdentifier: "ItemDetailsVC", sender: item)
        }
    }
    
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "ItemDetailsVC" {
            if let destination = segue.destination as? ItemDetailsVC {
                if let item = sender as? Item {
                    destination.itemToEdit = item
                }
            }
        }
        
    }
    
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        
        if let sections = controller.sections {
            
            let sectionInfo = sections[section]
            return sectionInfo.numberOfObjects
        }
        
        return 0
    }
    
    func numberOfSections(in tableView: UITableView) -> Int {
        
        return 0
    }
    
    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        
        return 150
    }

    func attemptFetch() {
        
        let fetchRequest: NSFetchRequest<Item> = Item.fetchRequest()
        let dateSort = NSSortDescriptor(key: "created", ascending: false)
        
        fetchRequest.sortDescriptors = [dateSort]
        
        let controller = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
        
        controller.delegate = self
        
        self.controller = controller
        
        do {
            
            try controller.performFetch()
            
        } catch {
            
            let error = error as NSError
            print("\(error)")
            
        }

    }
    
    func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
        tableView.beginUpdates()
    }
    
    func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
        tableView.endUpdates()
    }
    
    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
        
        switch(type) {
            
        case.insert:
            if let indexPath = newIndexPath {
                tableView.insertRows(at: [indexPath], with: .fade)
            }
            break
        case.delete:
            if let indexPath = indexPath {
                tableView.deleteRows(at: [indexPath], with: .fade)
            }
            break
        case.update:
            if let indexPath = indexPath {
                let cell = tableView.cellForRow(at: indexPath) as! ItemCell
                configureCell(cell: cell, indexPath: indexPath as NSIndexPath)
            }
            break
        case.move:
            if let indexPath = indexPath {
                tableView.deleteRows(at: [indexPath], with: .fade)
            }
            if let indexPath = newIndexPath {
                tableView.insertRows(at: [indexPath], with: .fade)
            }
            break
            
        }
    }
    
    
    func generateTestData() {
        
        let item = Item(context: context)
        item.title = "MacBook Pro"
        item.price = 1800
        item.details = "I can't wait until the September event, I hope they release new MPBs"
        
        let item2 = Item(context: context)
        item2.title = "Bose Headphones"
        item2.price = 300
        item2.details = "But man, its so nice to be able to block out everyone with the noise canceling tech."
        
        let item3 = Item(context: context)
        item3.title = "Tesla Model S"
        item3.price = 110000
        item3.details = "Oh man this is a beautiful car. And one day, I willl own it"
        
        
        ad.saveContext()
        
        
    }


}

ItemCell 的代码

import UIKit

class ItemCell: UITableViewCell {

    @IBOutlet weak var thumb: UIImageView!
    @IBOutlet weak var title: UILabel!
    @IBOutlet weak var price: UILabel!
    @IBOutlet weak var details: UILabel!
    
    func configureCell(item: Item) {
        
        self.title.text = item.title
        self.price.text = "$\(item.price)"
        self.details.text = item.details
        
    }
    
}

以及核心数据生成文件的代码

项目+CoreDataClass.swift

import Foundation
import CoreData


public class Item: NSManagedObject {
    
    public override func awakeFromInsert() {
        
        super.awakeFromInsert()
        
        self.created = NSDate()
    }
    
}

项目+CoreDataProperties.swift

import Foundation
import CoreData

extension Item {
    
    @nonobjc public class func fetchRequest() -> NSFetchRequest<Item> {
        return NSFetchRequest<Item>(entityName: "Item");
    }
    
    @NSManaged public var created: NSDate?
    @NSManaged public var details: String?
    @NSManaged public var title: String?
    @NSManaged public var price: Double
    @NSManaged public var toImage: Image?
    @NSManaged public var toItemType: ItemType?
    @NSManaged public var toStore: Store?
    
}

有什么想法或想法吗？提前致谢。

Answer 1

在核心数据文件中选择实体并选择 Codegen 选项进行类定义并运行并查看