如何迅速将核心数据管理对象数组转换为“可识别”列表？ （Xcode 11，Beta 5）

Question

How would one transfer an array of managed objects retrieved from Core Data using Swift/IOS via a "fetchRequest", to an array that is "identifiable"?

Example - How to make the "tasks" array "identifiable"

let fetchRequest : NSFetchRequest<Todo> = Todo.fetchRequest()
let tasks = try context?.fetch(fetchRequest)

Background:

• In SwiftUI using a "List" the array of data you pass to the List needs to be "identifiable".
• I also note the identified(by: .self) seems to be deprecated.
• Using (Xcode 11, Beta 5)
• Currently using xcode's automatic creation of managed objects for the core data entities, so would be nice to stick with this approach

Answer 1

Use replacement ForEach(Data, id: \\.idAttribute)

The feature identified(by: .self) was replaced with the new syntax:

ForEach(filteredGrapes, id: \.id) { grape in
    GrapeCell(grape: grape)
}

Coredata example:

Using a file named ItemStore.xcdatamodeld with an entity ItemDAO defined with Generation=Class Definition enabled and having a String-attribute named title .

Note: One has to Product/Clear Build Folder and afterwards restart Xcode to make Xcode11Beta5 find the proper key path, which seems to be a bug in Xcode11Beta5.

import Foundation
import SwiftUI
import CoreData

class MyItemStore {
    public static func defaultItems() -> [ItemDAO]{
        let store = NSPersistentContainer(name: "ItemStore")
        store.loadPersistentStores { (desc, err) in
            if let err = err {
                fatalError("core data error: \(err)")
            }
        }
        let context = store.viewContext
        let item = ItemDAO(context: context)
        item.title = "hello you"
        try! context.save()
        return [
            item,
            item,
        ]
    }
}

struct CoreDataView: View {
    let items: [ItemDAO] = MyItemStore.defaultItems()

    var body: some View {
        VStack{
            ForEach(items, id: \.title) { (item: ItemDAO) in
                Text(item.title ?? "no title")
            }
            Text("hi")
        }
    }
}

Adding Identifiable via Extension

extension Todo: Identifiable {
    public var id: String {
        //return self.objectID.uriRepresentation().absoluteString
        return self.title!
    }
}

Maintaining CoreData models manually to add Identifiable

There you can add Identifiable as usual, which is not necessary though since an extension can add Identifiable too.