SwiftData mode does not update the view when I insert child records

Question

I have a problem with SwiftData and inserting child records. The insert itself works but the views are not updated. If I add a new court record in DetailView, tournament.title in ContentView changes to Tournament with new court but tournament.courts.count is still 1 and not 2, 3, … Also the List in DetailView shows only the initial court and not the new added.

The ist only a view problem. If I start the app again, it looks fine and all added courts are shown.

Any idea how I can refresh the view after adding or changing child records?

This is like my models and code looks like:

Tournament model:

@Model
final class Tournament {
    var title: String
    @Relationship(deleteRule: .cascade, inverse: \Court.tournament) var courts: [Court]
    
    init(title: String, courts: [Court] = []) {
        self.title = title
        self.courts = courts
    }
}

Court model:

@Model
final class Court {
    @Relationship var tournament: Tournament
    var number: Int
    
    init(tournament: Tournament, number: Int) {
        self.tournament = tournament
        self.number = number
    }
}

ContentView:

struct ContentView: View {
    @Environment(\.modelContext) private var modelContext
    @Query var tournaments: [Tournament]
    @State var selectedTournament: Tournament?
    
    var body: some View {
        NavigationSplitView {
            List(selection: $selectedTournament) {
                ForEach(tournaments) { tournament in
                    NavigationLink(value: tournament) {
                        HStack {
                            Text("\(tournament.title)")
                            Spacer()
                            Text("(\(tournament.courts.count))")
                        }
                    }
                }
            }
            .toolbar {
                ToolbarItem {
                    Button(action: {
                        addTournament()
                    }) {
                        Label("Add tournament", systemImage: "plus")
                    }
                }
            }
        } detail: {
            DetailView(tournament: selectedTournament)
        }
    }
    
    private func addTournament() {
        let newTournament = Tournament(title: "New tournament")
        modelContext.insert(newTournament)
        
        let court = Court(tournament: newTournament, number: 1)
        modelContext.insert(court)
        
        try? modelContext.save()
    }
}

DetailView:

struct DetailView: View {
    @Environment(\.modelContext) private var modelContext
    var tournament: Tournament?
    
    var body: some View {
        if let tournament {
            List {
                Section(tournament.title) {
                    ForEach(tournament.courts) { court in
                        Text("\(court.number)")
                    }
                }
            }
            Button {
                addCourt()
            } label: {
                Text("Add court")
            }
        } else {
            emptyView // ContentUnavailableView
        }
    }
    
    func addCourt() {
        if let tournament {
            let newCourt = Court(tournament: tournament, number: tournament.courts.count+1)
            modelContext.insert(newCourt)
        
            tournament.title = "Tournament with new court"
        
            try? modelContext.save()
        }
    }
}

Update

I found a solution but I don’t know why this works. If I change both relations to optional, the views will be refreshed on adding records.

@Model
final class Tournament {
    var title: String
    @Relationship(deleteRule: .cascade, inverse: \Court.tournament) var courts: [Court]?
    …
}

@Model
final class Court {
    var tournament: Tournament?
    …

Thanks! You are right and with this it’s easier to handle the courts. — Babelfish
– Babelfish, Commented Aug 4, 2024 at 20:58

Babelfish · Accepted Answer · 2024-08-04 21:01:33Z

2

The problem is solved with defining the tournament property in Court as optional.

@Model
final class Court {
    var tournament: Tournament?
    …

answered Aug 4, 2024 at 21:01

Babelfish

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2 Comments

Joakim Danielson Over a year ago

If this answer solved the problem then mark it as accepted please so it’s clear the question has been properly answered.

Babelfish Over a year ago

Done! But I was able to mark the correct answer after three days.

Tob · Accepted Answer · 2024-08-04 16:21:35Z

0

This is a bit tricky.

Try to take the set out of the tournament add the court to the set and use tournament.courts = newCourts

The problem is, that the setter is on the court side. I’m actually not sure if it helps, but this is how I understand the underlying fetch result.

answered Aug 4, 2024 at 16:21

Tob

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5 Comments

Babelfish Over a year ago

Settings tournament.courts directly will cause a fatal error: Fatal error: Unsupported relationship key path ReferenceWritableKeyPath<Court, Tournament>

Tob Over a year ago

Oh man, check this one out: stackoverflow.com/questions/76987282/…

Tob Over a year ago

Or try to mark it as bindable.

Babelfish Over a year ago

Thanks, but I know this answer and the given answer is wrong. Any @Model is also @Observable by default. There is no different if I wrap the model in a view model or not. The result is the same. What did you mean with bindable in context of a SwiftData model?

Tob Over a year ago

Sometimes it’s enough to do @Bindable let tournament before passing

malhal · Accepted Answer · 2024-08-06 12:03:27Z

0

You are missing another @Query for courts with a predicate to find the courts in the specific tournament, e.g.


    @Query var courts: [Court]

    init(tournamentID: Tournament.ID) {
        let predicate = #Predicate<Court> {
            $0.tournament.persistentModelID = tournamentID
        }
        _courts = Query(filter: predicate, sort: \Court.date)
    }

edited Aug 6, 2024 at 12:03

answered Aug 4, 2024 at 17:32

malhal

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8 Comments

Babelfish Over a year ago

@Query gets all courts but I need only the courts for the current tounament record. So this is not the right way. See my update at the end of the question.

malhal Over a year ago

No your @Query is for tournaments, you are missing another @Query for courts

Babelfish Over a year ago

Please look at the code. There is a relationship between Tournament and Court. With @Query I can’t get the related courts for this tournament. BTW: I have updated the question and the solition for the problem is that one oft the realtionships must be optional.

malhal Over a year ago

You can use the Query predicate for that

Babelfish Over a year ago

I can’t use the predicate in this case and there is no reason to add an additional @Query. I’ve posted the solution as extra answer to my question. The problem was that the one-property of a one-to-many relationship must be optional.

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