无法使用非集合对象执行集合评估

Question

当我执行 segue 时，我将所有季节从一个选定的节目传递到下一个 ViewController。

class ShowsViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        // Request Items with type = Movie
        let request: NSFetchRequest<TelevisionShow> = TelevisionShow.fetchRequest()
        allShows = try! CoreDataStack.context.fetch(request)
        allShows = allShows.sorted(by: { [=10=].title! <  .title! })
    }

    @IBOutlet private weak var collectionView: UICollectionView!
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

        // Create a variable that you want to send based on the destination view controller

        selectedShow = allShows[indexPath.item]

        // This will perform the segue and pre-load the variable for you to use
        self.performSegue(withIdentifier: "toSeasonsViewController", sender: self)

    }

如果我尝试使用 NSPredicate 获取请求，我会崩溃。 (2019-02-04 11:10:48.766456+0100 电视[16295:659978] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Can't perform collection evaluate with non-collection object.')

class SeasonsViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let request: NSFetchRequest<Season> = Season.fetchRequest()
        request.returnsObjectsAsFaults = false
        request.predicate = NSPredicate(format: "SUBQUERY(televisionShow, $m, ANY $m.seasons IN %@).@count > 0",(pTelevisionShow?.seasons)!)

        allSeasons = try! CoreDataStack.context.fetch(request)
        allSeasons = allSeasons.sorted(by: { [=11=].number! <  .number! })
    }

    @IBOutlet private weak var collectionView: UICollectionView!

    var pTelevisionShow: TelevisionShow?
}

问题是我第一次选择一个电视节目并执行 segue 时，它运行良好，如果我返回并选择另一个电视节目，它会抛出该错误。

+

class AppDelegate: UIResponder, UIApplicationDelegate { Thread 1: signal SIGABRT

libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)

pTelevisionShow?.seasons 是 NSOrderedSet

解决方案：

allSeasons = pTelevisionShow?.seasons!.sorted(by: { ([=13=] as! Season).number! < ( as! Season).number! }) as! [Season]

Answer 1

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Can't perform collection evaluate with non-collection object.')

看起来您的谓词返回的是单个对象而不是对象集合。

因此您的谓词逻辑 NSPredicate(format: "SUBQUERY(televisionShow, $m, ANY $m.seasons IN %@).@count > 0",(pTelevisionShow?.seasons)!) 出于某种原因返回单个元素。

但是，在您的情况下，由于您要向前传递 pTelevisionShow，您的结构已经引用了所需的 seasons 数据集并且可以直接访问，因此您不需要fetchRequest 再次 Season。

删除以下代码：

let request: NSFetchRequest<Season> = Season.fetchRequest()
request.returnsObjectsAsFaults = false
request.predicate = NSPredicate(format: "SUBQUERY(televisionShow, $m, ANY $m.seasons IN %@).@count > 0",(pTelevisionShow?.seasons)!)

更改并保留：

allSeasons = pTelevisionShow?.seasons.sorted(by: { [=11=].number! < .number! })

无法使用非集合对象执行集合评估

Can't perform collection evaluate with non-collection object

swift

core-data

nsorderedset