SQLite GRDB topics

[morstin]

@mbrandonw @stephencelis : Dear Brandon, Dear Stephen: thrilled that you are picking up SQLite / GRDB in your most recent episode. If you find time in this series, I would very interested in your take on:

• How to conform the table structs as Player, Team to Identifiable?
  What's the "right" way to use autoIncrementedPrimaryKey? groue/GRDB.swift#1435
  When using those structs in SwiftUI Lists / IdentifiedArrays this would be very helpful.

• How to keep database consistency when deleting?
  Deleting in a many-to-many relationship groue/GRDB.swift#1609
  https://forums.swift.org/t/grdb-persistence-callback-diddelete-gives-no-db/74829

Thank you very much for the great series!

[mbrandonw]

Hi @morstin, I don't think there are any universal, correct solutions to these problems.

How to conform the table structs as Player, Team to Identifiable?

While I understand why it can be strange to have an optional ID in an Identifiable conformance, I do think it is the more pragmatic approach to just do it anyway. SwiftUI demands identifiable types, and auto-increment keys demands optionality. So you are stuck between a rock and a hard place.

So I personally think it is ok to conform to Identifiable and just remember that all un-persisted records have the same identity.

If you are willing to use macros you might be able to create some kind of @Draftable macro for creating "draft" versions of your model:

@Draftable
struct Player {
  var id: Int64
  var name: String
}

// expands to:
struct Player {
  var id: Int64
  var name: String

  struct Draft {
    var id: Int64?
    var name: String
  }
}

Then when creating players you can use Player.Draft. I still think there are substantial ergonomics problems to think through before this can be viable.

How to keep database consistency when deleting?

I don't think we are going to have much to say about this. Only thing that comes to mind is adding a SQLite trigger to execute when songs are deleted to then clean up empty albums. But this really isn't going to be the focus of our explorations.

[morstin]

@mbrandonw Thank you for your quick response; I really appreciate it!