CODEWITHSUNDEEP
swiftcore-dataswiftui
Timo Müller
Timo Müller

Reputation: 11

Accessing property is not possible

I want to display a separate SubjectView in the MainView.

The property topics on subject in SubjectView is not accessible.

What should I do about it? Thanks.

Update:

ForEach(subject.topics, id: \.self) { topic in
    Text(topic.title)
}

... could be the problematic part.

File: SubjectView

import SwiftUI

struct SubjectView: View {
    @State var subject: Subject
    
    var body: some View {
        List {
            ForEach(subject.topics, id: \.self) { topic in
                Text(topic.title)
            }
        }
    }
}

File MainView

import SwiftUI

struct MainView: View {
    @Environment(\.managedObjectContext) var managedObjectContext
    
    @FetchRequest(entity: Subject.entity(), sortDescriptors: [NSSortDescriptor(keyPath: \Subject.name, ascending: true)]) var subjects: FetchedResults<Subject>
    
    @State var subjectName: String = ""
    
    var body: some View {
        NavigationView {
            Form {
                List {
                    ForEach(subjects, id: \.self) { subject in
                        NavigationLink(
                            destination: SubjectView(subject: subject),
                            label: {
                                Text(subject.name ?? "-")
                            })
                    }
                }
            }
            .navigationTitle("Schulfächer")
        }
    }
}

Screenshot of the Subject entity

The error at SubjectView: var body: some View reads:

Failed to produce diagnostic for expression; please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the project

Upvotes: 0

Views: 76

Answers (2)

lorem ipsum
lorem ipsum

Reputation: 29309

@State var subject: Subject

in SubjectView should be

@ObservedObject var subject: Subject

https://developer.apple.com/documentation/swiftui/managing-model-data-in-your-app

@StateObject is for initializing ObservableObjects

As for your topics

ForEach((subject.topics.allObjects as? [Topic]) ?? [], id: \.self) { topic in

Should work

Upvotes: 0

vadian
vadian

Reputation: 285072

The collection type of ForEach must conform to RandomAccessCollection. topics does not because it's an (NS)Set.

A simple solution is to sort the Set which becomes an Array. Or create an array explicitly, the line assumes that topics is a native Swift Set<Topic>

Array(subject.topics)

Note: Do not use \.self carelessly. Determine one attribute which is unique and/or adopt Identifiable. For example you could use the NSManagedObjectID of the NSManagedObject instance which is unique.

Upvotes: 1

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