SwiftUI / CoreData /母版/明细（带有编辑）/ Xcode 11-Beta 5 [英] SwiftUI / CoreData / Master / Detail (with editing) / Xcode 11 - Beta 5

问题描述

使用示例应用程序。目的是要从MasterData中的CoreData中提取一个列表，然后单击一个以转到详细信息，您可以在其中编辑信息并保存。当编辑明细中的名称时，它不仅更新明细以反映更改，而且还反映了母版上的更改。我已经尝试了多种方法来实现此目的，但是到目前为止，还没有一个答案。

Working on a sample app. The goal is to have a list pulled up from CoreData in a Master, and then click on one to go to a detail, where you can edit the information and save. When you edit the "name" in the detail, it not only updates the detail to reflect the change, but it also reflects the change on the master as well. I've tried numerous ways to accomplish this, but so far have not come up with an answer.

// Code generation is turned OFF in the xcdatamodeld file

public class EntityName: NSManagedObject, Identifiable {
   @NSManaged public var name: String
   @NSManaged public var active: Bool
}

extension EntityName {
    static func allEntityNameFetchRequest() -> NSFetchRequest<EntityName> {
        let request: NSFetchRequest<EntityName> = EntityName.fetchRequest() as! NSFetchRequest<EntityName>
        request.sortDescriptors = [NSSortDescriptor(key: "name", ascending: true)]
        return request
   }
}


struct MasterView: View {

    @Environment(\.managedObjectContext) var managedObjectContext
    @FetchRequest(fetchRequest: EntityName.allEntityNameFetchRequest()) var allEntityNames: FetchedResults<EntityName>


    var body: some View {
        NavigationView {
            List {
                ForEach(self.allEntityNames) { entityName in
                NavigationLink(destination: DetailView(entityName: entityName)) {
                    VStack(alignment: .leading) {
                        Text(entityName.name)
                            .font(.headline)
                        Text(String(entityName.active))
                            .font(.subheadline)
                    }
                }
            }
        }
    }
    .onAppear() {
        // Just want to populate the Core Data to have a few to work with
        if self.allEntityNames.count == 0 {
            for _ in 1...3 {
                let newEntry = EntityName(context: self.managedObjectContext)
                newEntry.name = "New Entry"

                try! self.managedObjectContext.save()
            }
         }
      }
   }
}

struct DetailView: View {

   var entityName = EntityName()

   var body: some View {
       VStack {
           Text("Name: \(entityName.name)")
           Text("Active: \(String(entityName.active))")

           // What I'd like to do now:
              //TextField("", text: $entityName.name)
              //Toggle(isOn: $entityName.active)
       }
   }
}

推荐答案

如所承诺的，这是使用CoreData的示例SwiftUI程序的链接。当前版本可以在GM版本上编译并运行。它不使用新的@FetchRequest属性包装器，因为它不能满足我的所有需求。我编写了一个CoreDataDataSource类，该类基本上执行相同的操作，并且执行了更多操作。

As promised, here is a link to sample SwiftUI program that uses CoreData. The current version compiles and runs on the GM release. It does not use the new @FetchRequest property wrapper because it does not suit all of my needs. I wrote a CoreDataDataSource class that does basically the same thing plus a lot more.

https://github.com/Whiffer/SwiftUI-Core-Data-Test

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