SwiftData nested custom model CRASH

Question

@Model class AModel {
    @Attribute(.unique) var id:String
    var date:Date
    var b:[BModel]
    init() {
        self.id = UUID().uuidString
        self.date = Date()
        self.b = []
    }
}
@Model class BModel {
    @Attribute(.unique) var id:String
    var date:Date
    init() {
        self.id = UUID().uuidString
        self.date = Date()
    }
}

struct MainView: View {
    @Environment(\.modelContext) private var db
    @State private var a:AModel = AModel()
    
    var body: some View {
        VStack {

        }
        .onAppear {
            a.b.append(BModel())
            print(a.b)
        }
    }
}

// CRASH :
@Model class AModel {
    @Attribute(.unique) var id:String
    var date:Date
    var b:[BModel]
/**
Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
{
    get {
        _$observationRegistrar.access(self, keyPath: \.b)
        return self.getValue(for: \.b)
    }

    set {
        _$observationRegistrar.withMutation(of: self, keyPath: \.b) {
          self.setValue(for: \.b, to: newValue)
        }
    }
}
*/
    init() {
        self.id = UUID().uuidString
        self.date = Date()
        self.b = []
    }
}
@Model class BModel {
    @Attribute(.unique) var id:String
    var date:Date
    init() {
        self.id = UUID().uuidString
        self.date = Date()
    }
}

1.3k

Posted by

mandriao84

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Answer 1

I'm having this exact issue and am stumped. Hoping someone else chimes in.

Posted by

Razorback2424

I am also having the same issues.

—
CinnamonRage

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Answer 2

Same issue

Posted by

AaronIntohand

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Answer 3

Ok so two issues I can see here, forgive me if I'm wrong but I need to rush this answer

First up you're not using Relationships

@Model class AModel {
    @Attribute(.unique) var id:String
    var date:Date
    @Relationship(inverse: \BModel.aModel)
    var b:[BModel]
}

 
@Model class BModel {
    @Attribute(.unique) var id:String
    var date:Date
    var aModel: AModel?

    init() {
        self.id = UUID().uuidString
        self.date = Date()
    }
}

Secondly, and this is something that only started happening to me in the last two betas. I found I need to insert the bModel before appending it to a property in aModel. This may not be the issue, as usually this only affects me when passing a model through in an initialiser, but worth a shot

.onAppear {
    let model = BModel()
    modelContext.insert(model)
    a.b.append(model)
    print(a.b)
 }

Again, apologies if I misunderstood the question, I'm in a bit of a rush here. Let me know if I can help more

Posted by

skillbane

Not sure about the @mandriao84 , but this solution didn't work for me. I'm using the same classes as codable to handle API response. So BModel is only initialised inside AModel init(from decoder: Decoder). So your solution inside onAppear doesn't work in my case.

—
goswamirv00

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SwiftData nested custom model CRASH

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