ios - 发送到实例的 CoreData 无法识别的选择器

Question

我正在尝试将 CoreData 添加到我的应用程序中。这个应用程序将成为一个照片应用程序，并让用户能够将照片存储在相册中。我目前在 CoreData 中有两个实体，Photo 和 Album。

Album 实体有四个属性。 albumCoverImageData: 二进制数据, id: UUID, name: String, passwordProtected: Boolean。除了这些属性之外，它还有一个关系 photos destination Photo Inverse Album。

Photo实体有两个属性，id: UUID和imageData: BinaryData

在尝试向数据库添加新专辑时，在尝试保存上下文时，应用程序崩溃并出现以下错误。

2020-10-20 15:49:33.889808-0400 LockIt[902:92475] -[__NSConcreteUUID compare:]: unrecognized selector sent to instance 0x2817b4fe0

2020-10-20 15:53:28.604954-0400 LockIt[902:92475] [error] error: Serious application error.  Exception was caught during Core Data change processing.  This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.  -[__NSConcreteUUID compare:]: unrecognized selector sent to instance 0x2817b4fe0 with userInfo (null)

CoreData: error: Serious application error.  Exception was caught during Core Data change processing.  This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.  -[__NSConcreteUUID compare:]: unrecognized selector sent to instance 0x2817b4fe0 with userInfo (null)

2020-10-20 15:53:28.622315-0400 LockIt[902:92475] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSConcreteUUID compare:]: unrecognized selector sent to instance 0x2817b4fe0'

*** First throw call stack:

(0x1937c65ac 0x1a78b442c 0x1936d0a2c 0x1937c9130 0x1937cb420 0x194b18c90 0x1998e5dc8 0x1998e58a0 0x1998e6ad0 0x1998e77b4 0x19989a410 0x199767b64 0x1998e7100 0x193725764 0x193725718 0x193724cd4 0x1937246a0 0x1949bc5f4 0x199892118 0x1998a0c50 0x199892fc0 0x199761aa0 0x104503bd8 0x104502e68 0x104502854 0x199fd2c04 0x19a2c3ec0 0x19a049990 0x19a0499b8 0x19a049990 0x19a03a1dc 0x19a088444 0x19a4d8f58 0x19a4d71a4 0x19a4d7d78 0x195c4d334 0x196177a4c 0x195c43350 0x195c43030 0x19612ef80 0x196108bc0 0x196190118 0x196193070 0x19618a5f4 0x19374381c 0x193743718 0x193742a28 0x19373cd20 0x19373c4bc 0x1aa24e820 0x1960e9164 0x1960ee840 0x1044f2178 0x193403e40)

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

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSConcreteUUID compare:]: unrecognized selector sent to instance 0x2817b4fe0'

terminating with uncaught exception of type NSException

我在下面附上了相关文件。 照片+CoreDataProperties

import Foundation

import CoreData





extension Photo {



    @nonobjc public class func fetchRequest() -> NSFetchRequest<Photo> {

        return NSFetchRequest<Photo>(entityName: "Photo")

    }



    @NSManaged public var id: UUID?

    @NSManaged public var imageData: Data?

    @NSManaged public var album: Album?



}



extension Photo : Identifiable {



    public var wrappedID: UUID {

        id!

    }

    

    public var wrappedImageData: Data {

        imageData!

    }

}

专辑+CoreDataProperties

import Foundation

import CoreData





extension Album {



    @nonobjc public class func fetchRequest() -> NSFetchRequest<Album> {

        return NSFetchRequest<Album>(entityName: "Album")

    }



    @NSManaged public var albumCoverImageData: Data?

    @NSManaged public var id: UUID?

    @NSManaged public var name: String?

    @NSManaged public var passwordProtected: Bool

    @NSManaged public var photos: NSSet?

    

    public var wrappedID: UUID {

        id!

    }

    

    public var wrappedAlbumCoverImageData: Data {

        albumCoverImageData!

    }

    

    public var wrappedName: String {

        name ?? "Unamed Album"

    }

    

    public var wrappedPasswordProtected: Bool {

        passwordProtected

    }

    

    public var photoArray: [Photo] {

        let set = photos as? Set<Photo> ?? []

        

        return Array(set)

    }



}



// MARK: Generated accessors for photos

extension Album {



    @objc(addPhotosObject:)

    @NSManaged public func addToPhotos(_ value: Photo)



    @objc(removePhotosObject:)

    @NSManaged public func removeFromPhotos(_ value: Photo)



    @objc(addPhotos:)

    @NSManaged public func addToPhotos(_ values: NSSet)



    @objc(removePhotos:)

    @NSManaged public func removeFromPhotos(_ values: NSSet)



}



extension Album : Identifiable {

    

}

主视图

import SwiftUI



struct AlbumCollectionView: View {

    @Environment(\.managedObjectContext) var managedObjectContext

    @FetchRequest(entity: Photo.entity(),

                  sortDescriptors: [

                    NSSortDescriptor(keyPath: \Photo.id, ascending: true)

                  ]

    ) var photos: FetchedResults<Photo>

    

    @FetchRequest(entity: Album.entity(),

                  sortDescriptors: [

                    NSSortDescriptor(keyPath: \Album.name, ascending: true)

                  ]

    ) var albums: FetchedResults<Album>

    

    @State private var showingImagePicker = false

    @State private var showingPopover = false

    @State private var inputImage: UIImage?

    @State private var albumNameInput: String = ""

    

    let columns = [

        GridItem(.adaptive(minimum: 150))

    ]

    

    var body: some View {

        ScrollView {

            LazyVGrid(columns: columns, spacing: 20) {

                ForEach(albums) { album in

                    NavigationLink(destination: AlbumView(album: album)) {

                        VStack {

                            Image(data: album.albumCoverImageData, placeholder: "No Image")

                                .resizable()

                                .aspectRatio(1, contentMode: .fill)

                                .contextMenu(menuItems: {

                                    Button(action: {

                                        deleteAlbum(selectedAlbum: album)

                                    }) {

                                        Label("Remove", systemImage: "trash")

                                    }

                                })

                            Text(album.name ?? "")

                        }

                    }

                }

            }

            .padding()

            .navigationBarTitle(Text("Albums"))

            .navigationBarItems(trailing:

                Menu {

                    Button(action: {

                        self.showingPopover = true

                    }) {

                        Label("Add Album", systemImage: "photo.on.rectangle.angled")

                    }

                    Button(action: {

                        self.showingImagePicker = true

                    }) {

                        Label("Add Photo", systemImage: "photo")

                    }

                } label: {

                    Image(systemName: "plus")

                        .popover(isPresented: $showingPopover, arrowEdge: .trailing ,content: {

                            VStack {

                                Text("New Album")

                                TextField("Enter Album Name",text: $albumNameInput)

                                    .textFieldStyle(RoundedBorderTextFieldStyle())

                                Button("Submit"){

                                    addAlbum(name: albumNameInput, albumCover: UIImage(named: "Image 1")!)

                                    albumNameInput = ""

                                    showingPopover = false

                                }

                            }

                            .padding()

                        })

                }

            )

            .sheet(isPresented: $showingImagePicker, onDismiss: loadImage) {

                ImagePicker(image: self.$inputImage)

            }

        }

    }

    

    func addAlbum(name: String, albumCover: UIImage) {

        let newAlbum = Album(context: managedObjectContext)

        

        newAlbum.id = UUID()

        newAlbum.name = name

        newAlbum.passwordProtected = false

        newAlbum.albumCoverImageData = albumCover.jpegData(compressionQuality: 1.0)

        

        saveContext()

    }

    

    func deleteAlbum(selectedAlbum: Album) {

        for album in albums {

            if selectedAlbum == album {

                self.managedObjectContext.delete(album)

            }

        }

        saveContext()

    }

    

    func loadImage() {

        guard let inputImage = inputImage else { return }

        addPhoto(image: inputImage)

    }

    

    func addPhoto(image: UIImage) {

        let newPhoto = Photo(context: managedObjectContext)

        

        newPhoto.id = UUID()

        newPhoto.imageData = image.jpegData(compressionQuality: 1.0)

        

        saveContext()

    }

    

    func saveContext() {

        do {

            try managedObjectContext.save()

        } catch {

            print("Error saving managed object context: \(error)")

        }

    }

}

我不知道这里会发生什么，感谢任何见解!

Answer 1

您说添加和保存新 Album 时会出现问题，但我认为问题实际上与 Photos 有关。错误:

reason: '-[__NSConcreteUUID compare:]: unrecognized selector sent to instance

使用的是旧的 Objective-C 术语(CoreData 的核心是基于 Objective-C)。它表明存在 __NSConcreteUUID 类型的对象(可能是 CoreData 用来存储 UUID 的对象类型)并且 CoreData 正在尝试调用 compare 方法那个物体。 compare 是在对对象进行排序时调用的方法:比较对象 A 和对象 B 以确定它们应该相对于彼此放置的顺序。

因此，问题的根源在于您的 View 正在按 UUID 对某些内容进行排序，而这似乎是照片:

     @FetchRequest(entity: Photo.entity(),
         sortDescriptors: [
             NSSortDescriptor(keyPath: \Photo.id, ascending: true)
             ]
         ) var photos: FetchedResults<Photo>

但 UUID 不能以这种方式排序。除非有充分的理由按 UUID 排序，否则我只会更改排序顺序以使用不同的属性。