ios - 快速将核心数据检索到 TableView 单元格中

Question

我正在尝试简单地存储和检索 CoreData(我之前使用 swift 成功完成的事情)。我得到的数据为 nil，但现在(不确定发生了什么变化)我没有收到错误，只是在 tableview 中没有显示任何内容。我不确定存储或检索对象是否有问题。我已经尽可能详细地了解了我在我的另一个应用程序中是如何做到的，但似乎有一些基本的东西我没有得到。这是我的。

我的模型:

import Foundation
import CoreData

@objc(DataModel)
class DataModel: NSManagedObject {

@NSManaged var itemName: String
@NSManaged var quantity: NSNumber
@NSManaged var price: NSNumber

}

在我的带有文本字段静态单元格的 tableviewcontroller 中，我想从中保存数据:

import UIKit
import CoreData

class NewItemTableViewController: UITableViewController {

@IBOutlet weak var itemNameTextField: UITextField!
@IBOutlet weak var itemPriceTextField: UITextField!
@IBOutlet weak var itemQuantityTextField: UITextField!


override func viewDidLoad() {
    super.viewDidLoad()

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}


@IBAction func saveButton(sender: AnyObject) {
    //CoreData
    let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
    let managedContext : NSManagedObjectContext = appDelegate.managedObjectContext!
    let entity =  NSEntityDescription.entityForName("Item", inManagedObjectContext: managedContext)

    var newItem = DataModel(entity: entity!, insertIntoManagedObjectContext: managedContext)


    newItem.itemName = itemNameTextField.text
    //newItem.price = itemPriceTextField.text
    //newItem.quantity = itemQuantityTextField
    managedContext.save(nil)

    self.navigationController?.popToRootViewControllerAnimated(true)


}
@IBAction func cancelButton(sender: AnyObject) {
    self.navigationController?.popToRootViewControllerAnimated(true)
}

在我的 tableviewcontroller 中，我想检索动态单元格中显示的数据:

class ItemListTableViewController: UITableViewController {

var items : Array<AnyObject> = []

override func viewDidLoad() {
    super.viewDidLoad()
}



override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

// MARK: - Table view data source

override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    // #warning Potentially incomplete method implementation.
    // Return the number of sections.
    return 1
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    // #warning Incomplete method implementation.
    // Return the number of rows in the section.
    return items.count
}


override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    let CellID: NSString = "cell"
    var cell: UITableViewCell = tableView.dequeueReusableCellWithIdentifier(CellID) as UITableViewCell
    var data: NSManagedObject = items[indexPath.row] as NSManagedObject


    var itemName = data.valueForKey("itemName") as String
    var price = data.valueForKey("price") as NSNumber
    var quantity = data.valueForKey("quantity") as NSNumber


    cell.textLabel!.text! = "\(itemName)"
    cell.detailTextLabel!.text! = "Price: \(price) - Quantity: \(quantity)"

    return cell

}

对于我可能在此处某处遗漏的概念的任何帮助，我们将不胜感激!谢谢。

更新:所以我重做了我的代码以按照@Bluehound 的建议进行建模。但我仍然收到错误消息:不确定如何解决。

Answer 1

当使用核心数据和 TableView 时，您应该使用NSFetchedResultsController。这实质上是从核心数据中检索数据并按部分和索引路径组织它，因此可以轻松将其设置为 tableView 的数据源。这是一个符合 NSFetchedResultsControllerDelegate 的潜在 UITableViewController 的完整实现:​​

import Foundation
import UIKit
import CoreData


class HomeViewController: UITableViewController, NSFetchedResultsControllerDelegate {

    let managedObjectContext: NSManagedObjectContext? = (UIApplication.sharedApplication().delegate as? AppDelegate)?.managedObjectContext

    var fetchedResultsController: NSFetchedResultsController?

    override func viewDidLoad() {
        super.viewDidLoad()

        fetchedResultsController = NSFetchedResultsController(fetchRequest: allEmployeesFetchRequest(), managedObjectContext: managedObjectContext!, sectionNameKeyPath: nil, cacheName: nil)
        fetchedResultsController?.delegate = self
        fetchedResultsController?.performFetch(nil)


    }

    func allEmployeesFetchRequest() -> NSFetchRequest {

        var fetchRequest = NSFetchRequest(entityName: "Employee")
        let sortDescriptor = NSSortDescriptor(key: "nameLast", ascending: true)

        fetchRequest.predicate = nil
        fetchRequest.sortDescriptors = [sortDescriptor]
        fetchRequest.fetchBatchSize = 20

        return fetchRequest
    }

    //MARK: UITableView Data Source and Delegate Functions
    override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
        return fetchedResultsController?.sections?.count ?? 0
    }

    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

        return fetchedResultsController?.sections?[section].numberOfObjects ?? 0
    }

    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("HomeCell", forIndexPath: indexPath) as UITableViewCell

        if let cellContact = fetchedResultsController?.objectAtIndexPath(indexPath) as? Employee {
            cell.textLabel?.text = "\(cellContact.nameLast), \(cellContact.nameFirst)"

        }


        return cell
    }

    //MARK: NSFetchedResultsController Delegate Functions
    func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {

        switch type {
        case NSFetchedResultsChangeType.Insert:
            tableView.insertSections(NSIndexSet(index: sectionIndex), withRowAnimation: UITableViewRowAnimation.Fade)
            break
        case NSFetchedResultsChangeType.Delete:
            tableView.deleteSections(NSIndexSet(index: sectionIndex), withRowAnimation: UITableViewRowAnimation.Fade)
            break
        case NSFetchedResultsChangeType.Move:
            break
        case NSFetchedResultsChangeType.Update:
            break
        default:
            break
        }
    }

    override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
        if editingStyle == .Delete {
        }

        switch editingStyle {
        case .Delete:
            managedObjectContext?.deleteObject(fetchedResultsController?.objectAtIndexPath(indexPath) as Employee)
            managedObjectContext?.save(nil)
        case .Insert:
            break
        case .None:
            break
        }

    }

    func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {

        switch type {
        case NSFetchedResultsChangeType.Insert:
            tableView.insertRowsAtIndexPaths(NSArray(object: newIndexPath!), withRowAnimation: UITableViewRowAnimation.Fade)
            break
        case NSFetchedResultsChangeType.Delete:
            tableView.deleteRowsAtIndexPaths(NSArray(object: indexPath!), withRowAnimation: UITableViewRowAnimation.Fade)
            break
        case NSFetchedResultsChangeType.Move:
            tableView.deleteRowsAtIndexPaths(NSArray(object: indexPath!), withRowAnimation: UITableViewRowAnimation.Fade)
            tableView.insertRowsAtIndexPaths(NSArray(object: newIndexPath!), withRowAnimation: UITableViewRowAnimation.Fade)
            break
        case NSFetchedResultsChangeType.Update:
            tableView.cellForRowAtIndexPath(indexPath!)
            break
        default:
            break
        }
    }

    func controllerWillChangeContent(controller: NSFetchedResultsController) {
        tableView.beginUpdates()
    }

    func controllerDidChangeContent(controller: NSFetchedResultsController) {
        tableView.endUpdates()
    }
}

See a sample GitHub project here.