ios - 使用 Swift 自动重新排序 Core Data 中的 UICollectionView

Question

我有一个使用 UICollectionView 的应用程序，当用户点击并按住一个单元格时，它允许用户四处移动并重新排序该单元格的位置(类似于 iOS 允许您在主屏幕上重新排序应用程序的方式) .

当然，顺序的更改不会保存，当您离开 View 再回来时，它会恢复到原来的顺序。我的印象是有一种方法可以自动在 UITableView 中保存新的单元格顺序，而无需在 Core Data 中明确写出所有内容。

如何在 UICollectionView 中执行此操作？或者这是不可能的，我必须手动将所有内容写入核心数据？

编辑:当前相关代码:

@IBOutlet weak var groupCollection: UICollectionView!
var longPressGesture : UILongPressGestureRecognizer?
var newGroupOrderNum : Int?
let indexPath : IndexPath = []
var aryGroup : NSMutableArray!

func handleLongGesture(gesture: UILongPressGestureRecognizer) {

    switch(gesture.state) {

    case UIGestureRecognizerState.began:
        guard let selectedIndexPath = self.groupCollection.indexPathForItem(at: gesture.location(in: self.groupCollection)) else {
            break
        }
        groupCollection.beginInteractiveMovementForItem(at: selectedIndexPath)
    case UIGestureRecognizerState.changed:
        groupCollection.updateInteractiveMovementTargetPosition(gesture.location(in: gesture.view!))
    case UIGestureRecognizerState.ended:
        groupCollection.endInteractiveMovement()
        var timestamp: Date {
            return Date()
        }
        let creationTime = timestamp

        let appDelegate = UIApplication.shared.delegate as! AppDelegate
        let managedContext = appDelegate.managedObjectContext
        let entity =  NSEntityDescription.entity(forEntityName: "Group", in:managedContext)
        let group = NSManagedObject(entity: entity!, insertInto: managedContext)

        let orderChangeGroup = aryGroup.object(at: indexPath.row)
        group.setValue(orderChangeGroup, forKey: "groupOrderNum")

        do {
            try managedContext.save()
        }
        catch let error as NSError  {
            print("Could not save \(error), \(error.userInfo)")
        }

        group.setValue(creationTime, forKey: "creationTime")
    default:
        groupCollection.cancelInteractiveMovement()
    }
}

Answer 1

我认为您需要在订购完成后手动将其保存到 Core Data:

let context = self.fetchedResultsController.managedObjectContext
let event = self.fetchedResultsController.object(at: indexPath)
event.ordering = indexPath.row
do { try context.save() }
catch { }