@FetchOne / Draft pattern with dependent relationships (Property -> Room -> Item)

[StewartLynch]

My Database is Properties >> Rooms >> Items so one more level of relationship beyond the Reminders app example.
See ER diagram
When I am creating a new item using an ItemForm view, I create the Item.Draft so that I can either create a new Item or update an existing item.

I want to be able to change both the property and the room when creating or editing an item.
In my ItemForm view I believe I need both a selectedProperty as a Prioperty.Draft which is fine, but I also need to create a selectedRoom which is a Room.Draft. The problem is, that the Room.Draft needs the selectedProperty.id
I know that the below is wrong, and I need to create an initializer for the selectedRoom, but I am struggling to figure out how to do that and at the same time, I need to be able to fetch all of the rooms for hat selectedProperty
A big ask I am sure so any tips would be greatly appreciated.

@State var item: Item.Draft
@FetchOne var selectedProperty = Property.Draft()
@FetchOne var selectedRoom = Room.Draft(propertyID: selectedProperty.id)
@FetchAll(Property.order(by: \.name)) var properties
@FetchAll(
    Room
        .where{$0.id == selectedRoom.propertyID}
)

[stephencelis]

@StewartLynch If this is a dynamic form, where relations/rows may not be inserted yet, @FetchAll and @FetchOne may not be appropriate for loading the editable data. Instead, you can manually load the data into draft structures and then in a save action you can manually write back to the database.

While not exactly your situation, the reminders form is a good example of creating/updating a reminder using a draft, and then batching the write in a single transaction so that tags can be written with the foreign key.

Let us know if you have any questions, though!

[StewartLynch]

Yes, thanks for this. I have it working now. I pass in the current property from the presenting view and all is good now.