ios - 如何移动核心数据中的行 - 使用Faulting教程 - IOS

Question

我使用这个教程Faulting用于创建列表列表

现在我想在 ListView Controller 中移动行。

它成功移动了行，但我无法保存这些更改

我尝试了很多解决方案都没有效果。

请帮助我

import UIKit
import CoreData

class ListViewController: UIViewController, UITableViewDataSource, UITableViewDelegate, NSFetchedResultsControllerDelegate {

let ReuseIdentifierItemCell = "ItemCell"

@IBOutlet weak var tableView: UITableView!

var list: List!

var managedObjectContext: NSManagedObjectContext {
    get {
        return list.managedObjectContext!
    }
}

lazy var fetchedResultsController: NSFetchedResultsController = {
    // Initialize Fetch Request
    let fetchRequest = NSFetchRequest(entityName: "Item")

    // Add Sort Descriptors
    let sortDescriptor = NSSortDescriptor(key: "name", ascending: true)
    fetchRequest.sortDescriptors = [sortDescriptor]

    // Predicate
    let predicate = NSPredicate(format: "%K == %@", "list", self.list)
    fetchRequest.predicate = predicate

    // Initialize Fetched Results Controller
    let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.managedObjectContext, sectionNameKeyPath: nil, cacheName: nil)

    // Configure Fetched Results Controller
    fetchedResultsController.delegate = self

    return fetchedResultsController
}()

// MARK: -
// MARK: View Life Cycle
override func viewDidLoad() {
    super.viewDidLoad()

    do {
        try self.fetchedResultsController.performFetch()
    } catch {
        let fetchError = error as NSError
        print("\(fetchError), \(fetchError.userInfo)")
    }
}

// MARK: -
// MARK: Table View Data Source Methods
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    if let sections = fetchedResultsController.sections {
        return sections.count
    }

    return 0
}

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    if let sections = fetchedResultsController.sections {
        let sectionInfo = sections[section]
        return sectionInfo.numberOfObjects
    }

    return 0
}

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

    // Configure Table View Cell
    configureCell(cell, atIndexPath: indexPath)

    return cell
}

func configureCell(cell: UITableViewCell, atIndexPath indexPath: NSIndexPath) {
    // Fetch Item
    let item = fetchedResultsController.objectAtIndexPath(indexPath) as! Item

    // Update Cell
    cell.textLabel!.text = item.name
}

func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool {
    return true
}

func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
    if (editingStyle == .Delete) {
        // Fetch Item
        let item = fetchedResultsController.objectAtIndexPath(indexPath) as! Item

        // Delete Item
        self.managedObjectContext.deleteObject(item)
    }
}

// MARK: -
// MARK: Table View Delegate Methods
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
    tableView.deselectRowAtIndexPath(indexPath, animated: true)
}

// MARK: -
// MARK: Fetched Results Controller Delegate Methods
func controllerWillChangeContent(controller: NSFetchedResultsController) {
    tableView.beginUpdates()
}

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

func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
    switch (type) {
    case .Insert:
        if let indexPath = newIndexPath {
            tableView.insertRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
        }
        break;
    case .Delete:
        if let indexPath = indexPath {
            tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
        }
        break;
    case .Update:
        if let indexPath = indexPath {
            if let cell = tableView.cellForRowAtIndexPath(indexPath) {
                configureCell(cell, atIndexPath: indexPath)
            }
        }
        break;
    case .Move:
        if let indexPath = indexPath {
            tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
        }

        if let newIndexPath = newIndexPath {
            tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade)
        }
        break;
    }
}

// MARK: -
// MARK: Actions
@IBAction func addItem(sender: UIBarButtonItem) {
    let entityDescription = NSEntityDescription.entityForName("Item", inManagedObjectContext: self.managedObjectContext)

    // Initialize Item
    let item = Item(entity: entityDescription!, insertIntoManagedObjectContext: self.managedObjectContext)

    // Configure Item
    item.list = self.list
    item.name = "\(list.name!) - Item \(numberOfItems())"

    // Save Changes
    do {
        try self.managedObjectContext.save()
    } catch {
        let saveError = error as NSError
        print("\(saveError), \(saveError.userInfo)")
    }
}

// MARK: -
// MARK: Helper Methods
private func numberOfItems() -> Int {
    var result = 0

    if let items = self.fetchedResultsController.fetchedObjects {
        result = items.count
    }

    return result
}

}

谢谢

Answer 1

好吧，我们在错误之后修改了这段代码:

之前:

        let sortDescriptor = NSSortDescriptor(key: "position", ascending: true)

之后:

        let sortDescriptor = NSSortDescriptor(key: "position", ascending: false)

谢谢大家