ios - 核心数据查询返回正确的值，但表格单元格为空

Question

我正在从Core Data中获取数据，在控制台中打印时返回的数据是正确的。但 TableView 总是返回空单元格。该对象存在，同时返回 numberOfRowsinSection 和正确的计数。找了好几个小时了，希望不是拼写错误。感谢任何帮助，代码如下。我尝试了 valueForKey 和 valueForKeypath 但没有成功谢谢!

import UIKit
import CoreData

class HistoryViewController: UITableViewController{

@IBOutlet var historyTableView: UITableView!
var activitiesHistory: [NSManagedObject] = []


override func viewDidLoad() {
    super.viewDidLoad()
    title = "Past Workouts"
    tableView.register(UITableViewCell.self, forCellReuseIdentifier: "historyCell")
    let entity = NSEntityDescription.entity(forEntityName: "Activity", in: CoreDataStack.context)
    let fetchRequest: NSFetchRequest<Activity> = Activity.fetchRequest()
    fetchRequest.entity = entity

    //let sortDescriptor = NSSortDescriptor(key: #keyPath(Activity.timestamp), ascending: true)
    //fetchRequest.sortDescriptors = [sortDescriptor]

    do {
        activitiesHistory = try CoreDataStack.context.fetch(fetchRequest)
        //print(activitiesHistory)


    } catch  let error{
        //handle error
        print(error)
    }
}




override func tableView(_ tableView: UITableView,
               numberOfRowsInSection section: Int) -> Int {
    return activitiesHistory.count
}

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let workout = activitiesHistory[indexPath.row]
    let cell = tableView.dequeueReusableCell(withIdentifier: "historyCell", for: indexPath)
    print(workout.value(forKey: "timestamp"))
    cell.textLabel?.text = workout.value(forKey: "timestamp")as? String

    //cell.textLabel?.text = "test"
    return cell
}
 }

Answer 1

这对我有用。

var activities: [Activity] = []

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    addData()

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

    do {
        activities = try context.fetch(Activity.fetchRequest())
    }
    catch {

    }
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return self.activities.count
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
    cell.textLabel?.text = self.activities[indexPath.row].timestamp

    return cell
}

Result