Assuming I have a to many relatioship Parent -> Children, is there a way to make a query for Parent but sort the array based on Children property? or how could I achieve that. No much tutorials around yet.

Thanks @magna, I have read that but I can't figure out how to achive the following:

in the main view I use @Query to fetch an array of parents with a predicate (there will be only one parent with this predicate).

Then pass this parent to another view by a NavigationLink.

From here when using ForEach($parent.children) there is not problem, but I would need that the array of children is sorted.

If I try to sort it the bindable would no longer work. I have tried different ways but it seems I can't find the right one.

How can I get Children sorted when fetching from Parent or what workaround

@Obelix thanks for pointing that out, I had found it anyway. This is the correct link: https://www.hackingwithswift.com/quick-start/swiftdata/

Markdown Link Syntax

Try this technique:

Click the link icon while composing your message. It looks like three chain links.

Enter a clever text description between the [] brackets. Enter the web address between the parentheses. ()

Example:

See -> [Clever Description](https: //hackingwithswift.com/quick-start/swiftdata/ )

In markdown, this resolves to:
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This gives your link a cleaner look in forum responses.

Keep Coding!

Thanks @Obelix I'll use the Markdown link syntax next time... my bad.

Regarding my problem. Let's assume I have an array of family with properties name and origin

[Bennett, Fletcher, Dawson, Spencer]

and each family has an array of four members called

[Susan, Adam, Henry, Laura]

[Eric, John, Jane, Monika]

[Anthony, Lucia, Anna, Maria]

[Karl, Alfred, Zara, Fiona]

Based on the following Fetch:

@Query(filter: #Predicate<Family> {family in
        family.name == "New Zealand", sort: \Family.name) var families : Family

        var body: some View {
        NavigationStack {
            List {
                 ForEach(family) {family  in
                    NavigationLink {
                        EditFamily(family: family)
                    } label: {
                        Text("Default Allocation")
                    }
                }
                }

in the EditFamily view the outcome woul be:

Family Name: Bennett

Member1 name: Laura

Member2 name: Henry

Member3 name: Susan

Member4 name: Adam

But I want them ordered:

Member1 name: Adam

Member2 name: Henry

Member3 name: Laura

Member4 name: Susan

I can't understand how to Query from Family the relationship People sorted by name.

P.S.: I am aware I could use computed property with get and set to return the array sorted like with Core Data, just curious to see if that can be done

I am fighting similar challenges when working with parent and children relationships and @Queries.

I believe there is currently no way to order the result by children properties when querying the parents.

However, what you could try is, that you are doing a second query filtering for all children where children parent is a specific parent and ordering the result as you prefer.

The computed property should also work but I believe this gets difficult when querying a lot of objects regarding performance.

@rockeby would like some order to his family tree:

I can't understand how to Query from Family the relationship People sorted by name.

I used some code from another example program I was working. Perhaps this example can help you understand a one-to-many relationship and how you can select objects from SwiftData, and sort them based on parameters from two different SwiftData models.

It's a long example. But I've annotated with lot o'comments.

Lumos!

Think of Hogwarts. Each House in Hogwarts has a number of student wizards. Each Wizard is in one house, but each house may have several Wizards.

House and Wizard Models

import SwiftData

@Model
class House {
    @Attribute(.unique) var name: String
    // If you delete a House, then DELETE all wizards in the house too.
    @Relationship(deleteRule: .cascade, inverse: \Wizard.house)
    var wizards: [Wizard] // each house has a number of Wizard students

    init(named: String) {  // basic initializer
        self.name = named
        self.wizards = []  // none at first
    }
}

@Model
class Wizard {
    var name:   String
    var house:  House? // Maybe a wizard doesn't have a house?
    init(named: String, ofHouse house: House?) {
        self.name  = named
        self.house = house
    }
}

House View

The answer to your question (above) is in the @Query macro below. This was some playing-around code, so I used emojis as variable names.

import SwiftData
import SwiftUI

// MARK: - Computed Variables
struct HouseView: View {
    @Environment(\.modelContext) var 🏰  // context = Hogwarts!

    // Get All Wizards in Hogwarts (the context)
    // Sort the results, first by house name, THEN by Wizard name.
    @Query( sort: [
        SortDescriptor(\Wizard.house?.name),
        SortDescriptor(\Wizard.name)
    ] )
    var 🧙🏽🧙🏽🧙🏽🧙🏽: [Wizard]  //  Accio!  (summon objects spell!)

    // All houses in the context.🏚️
    // Weird syntax, I know. First, get all the houses linked to all Wizards, excluding nils.
    // Next compact them into a Set, which removes duplicates.
    // THEN, turn the set back into an array, so it's easy to manipulate.
    var 🏚️🏚️🏚️: Array<House> { Array(Set(🧙🏽🧙🏽🧙🏽🧙🏽.compactMap{ $0.house })) }

    var body: some View {
        NavigationStack {
            VStack {
                HeaderView(🧙🏽count: 🧙🏽🧙🏽🧙🏽🧙🏽.count, 🏚️count: 🏚️🏚️🏚️.count)
                List {
                   ForEach (🧙🏽🧙🏽🧙🏽🧙🏽) { 👻 in
                        WizardView(🧙🏽: 👻)
                    }.onDelete(perform: obscuro🧙🏽) // swipe to delete
                }
                Text("Notice the order!").font(.largeTitle)
                    .navigationTitle("🏰 Rosters").navigationBarTitleDisplayMode(.inline)
                HStack {
                    Button { enrollWizards()    } label: { Text("Enroll") }
                    Button { homenumRevelio🧙🏽() } label: { Text("New Wizard")} // Spell: Homenum Revelio
                }
            }.buttonStyle(.borderedProminent)
            Spacer()
        }
    }
}

Helper Methods

This is an extension to the view code. It contains a few helper methods.

// MARK: - View Methods
extension HouseView {
    // Spell reveals the presence of another person
    private func homenumRevelio🧙🏽() {
        guard let 𝓧          = "ABCDEFGHJKLMNOP".randomElement() else { return }
        guard let random🏚️   = 🏚️🏚️🏚️.randomElement() else { return }
        guard let randomName = ["Rockby", "Luna", "Harry", "Obelix"].randomElement() else { return }
        // Reveal the presence!
        _ = Wizard(named: "\(String(describing: 𝓧))-\(randomName)", ofHouse: random🏚️)
    }

    // Hide or remove an object
    private func obscuro🧙🏽(_ indexSet: IndexSet) {
        for index in indexSet {
            let 🧙🏽 = 🧙🏽🧙🏽🧙🏽🧙🏽[index]
            // Magic! Pass the object to the model context and delete it.
            🏰.delete(🧙🏽)
        }
    }

    // this populates the house and Wizard objects. 1 to many relationships
    private func enrollWizards() {
        // Enroll Gryffindor ============================
        let gryffindor = House(named: "Gryffindor")
        🏰.insert(gryffindor )
        let _ = Wizard(named: "Hermione", ofHouse: gryffindor)
        let _ = Wizard(named: "Ginny",    ofHouse: gryffindor)
        let _ = Wizard(named: "Ron",      ofHouse: gryffindor)
        let _ = Wizard(named: "Harry",    ofHouse: gryffindor)

        // Enroll Hufflepuff ============================
        let hufflepuff = House(named: "Hufflepuff")
        🏰.insert(hufflepuff)
        let _ = Wizard(named: "Newton", ofHouse: hufflepuff)
        let _ = Wizard(named: "Pamona", ofHouse: hufflepuff)
        let _ = Wizard(named: "Cedric", ofHouse: hufflepuff)

        // Enroll Ravenclaw ============================
        let ravenclaw = House(named: "Ravenclaw")
        🏰.insert(ravenclaw  )
        let _ = Wizard(named: "Rowena", ofHouse: ravenclaw)
        let _ = Wizard(named: "Padma",  ofHouse: ravenclaw)
        let _ = Wizard(named: "Luna",   ofHouse: ravenclaw)
        let _ = Wizard(named: "Obelix", ofHouse: nil)
        // autosave!  Just insert, SwiftData does the magic of saving.
    }
}

Subview Structs

These are subviews used in the HouseView struct. They're included as extensions. Why? Extensions help you organize your code into similar functional areas: Computed Vars, Structures, Methods. If I have them, I'll also toss enums into their own extension as well.

This level of organization isn't necessary for small structs. But @twoStraws wrote a nice short article on how this technique is useful.

See -> Organizing your Views

// MARK: - Structs for Subviews
extension HouseView {
    private struct WizardView: View {
        var 🧙🏽:    Wizard
        var 🧙🏽🏚️ : String {
            🧙🏽.house != nil ? 🧙🏽.house!.name.padding(toLength: 14, withPad: " ", startingAt: 0) : "unk         "
        }
        var body: some View {
            HStack(alignment: .bottom) {
                Text("🧙🏽 "); Text(🧙🏽🏚️); Text(🧙🏽.name)
            }
        }
    }

    private struct HeaderView: View {
        let 🧙🏽count: Int
        let 🏚️count: Int
        var body: some View {
            HStack{  // inflect is very cool! Learn this technique.
                Spacer(); Text("^[\(🧙🏽count) Wizard](inflect: true)") // Cool! Wizard / Wizards!
                Spacer(); Text("^[\(🏚️count) House](inflect: true)"); Spacer()
            }.font(.caption2)
        }
    }
}

Keep Coding!

@Obelix, question on your (incredible) example above. In your House and Wizard Models, you include a reference to House in Wizard, which @twostraws does not do in his SwiftData project (there, Destination references Sight and adds @Relationship, but Sight has no mention of Destination). Is there a reason you do this? Perhaps unrelated, but you also initialize wizard in house (and vice versa), which isn't something done in the sample project either.

A few of us are struggling to delete the 'relationship' items in the SwiftData project challenge...wondering if you're onto something here.

https://www.hackingwithswift.com/forums/books/hacking-with-swiftdata-delete-a-sight/24119