SwiftData: Accessing collection from computed property forces dependency update ?!? and this compute property and so on... cycle

Question

Created Aug ’23

Replies 4

Boosts 0

Participants 1

If I comment let _ = entries everything goes well, but if not, accessing(not editing) the collection I don't know why forces the view update (dependency change in items) and with the view update the computed property checkingDate is triggered firing the view update... and so on. Cycle

Why accessing entries forces view update ? If I change let _ = entries for let _ = name everything goes well so I conclude that is a problem with collection...

Models:

@Model
final class Item {
    var name: String
    @Relationship(deleteRule:.cascade) var entries: [Entry]
    init(name: String) {
        self.name = name
        entries = []
    }
}

extension Item {
    @Transient var checkingDate: Date {
        let _ = entries // < -- !!!
        //...
        return Date()
    }
}

@Model final class Entry {
    var value: Int
    var date: Date
    init(value: Int, date: Date) {
        self.value = value
        self.date = date
    }
}

View:

struct ContentView: View {
    @Query(sort: \Item.name) private var items: [Item]
    @Environment(\.modelContext) private var context
    var body: some View {
        let _ = Self._printChanges()
        List{
            ForEach(items){item in
                Text("Name:\(item.name), checking date: \(item.checkingDate, format: Date.FormatStyle(date: .numeric, time: .standard))")
            }
        }
    }
}

Boost

Answer 1

quaternionboy OP

Aug ’23

https://github.com/quaternionboy/LifeKPIs-SwiftData-Data-Model

0

Answer 2

quaternionboy OP

Aug ’23

https://github.com/quaternionboy/LifeKPIs-SwiftData-Data-Model

0

Answer 3

quaternionboy OP

Aug ’23

https://github.com/quaternionboy/LifeKPIs-SwiftData-Data-Model/tree/Profiling-LifeKPIs-Tests

0

Answer 4

quaternionboy OP

Aug ’23

workaround

@Model
final class Item {
    var name: String
    var id: UUID
    @Relationship(deleteRule:.cascade, inverse: \Entry.item) var entries: [Entry]
    init(name: String) {
        self.name = name
        self.id = UUID()
        entries = []
    }
}

extension Item {
    private var _entries: [Entry]? {
        return try? self.context?.fetch(FetchDescriptor<Entry>(predicate:#Predicate<Entry>{
            $0.item.id == id},sortBy: [SortDescriptor(\Entry.date, order: .forward)]))
    }
}

extension Item {
    func checkingDate()->Date?{
        let _ = _entries
        //...
        return Date()
    }
}

But is really awkward not allowed directly to access the collection property inside one entity...

0