Async db manager initializer and GRDBQuery

[Jason-Abbott]

My needs are met by the @Query Demo App except that my PlayerRepository equivalent has an asynchronous initializer which isn’t usable, as far as I can tell, as a DatabaseContext.

It is asynchronous because it applies migrations from a @globalActor “Registry”.

I am a Swift app novice so there’s a reasonable chance I settled on anti-pattern 🙂 but what I have are basically these Xcode targets:

• App
• SharedLib (has the Registry)
• FeatureLib1
• FeatureLib2
• FeatureLib3

App depends on everything else, SharedLib depends on nothing (except GRDB), and the FeatureLibs depend only on SharedLib.

Each FeatureLib registers its own unique migrations (and various other non-GRDB things). This all works fine in unit tests but I’m wondering if I’ll need to approach it differently in order to use DatabaseContext and GRDBQuery.

(relevant code:)

private init(_ connection: any DatabaseWriter) async throws {
   self.connection = connection
   try await migrate()
}

private func migrate() async throws {
   var migrator = DatabaseMigrator()
   for m in coreMigrations { m.register(with: &migrator) }
   for m in await ProviderRegistry.migrations { m.register(with: &migrator) }
   try migrator.migrate(connection)
}

[Jason-Abbott]

Maybe the easy answer is to dispense with the registry notion and allow App, since it imports everything, to iterate the FeatureLibs in some sense to combine their migrations for the Repository without an Actor in the chain.

Barring a quick alternate solution for DatabaseContext, I’ll probably start down this path ...

[groue]

Hello @Jason-Abbott,

Is there something that prevents your app from waiting for the database to be migrated before registering the DatabaseContext?

Here is a quick and dirty sample code:

import GRDB
import GRDBQuery

struct LoaderView: View {
    // Initially nil, then not nil when the database is ready
    @State var databaseContext: DatabaseContext?
    
    var body: some View {
        Group {
            if let databaseContext {
                MyView().databaseContext(databaseContext)
            } else {
                ProgressView()
            }
        }
        .task {
            do {
                let dbQueue = try DatabaseQueue()
                try await Task.sleep(for: .seconds(1)) // migrate
                databaseContext = DatabaseContext.readWrite { dbQueue }
            } catch {
                databaseContext = DatabaseContext.readWrite { throw error }
            }
        }
    }
}

struct MyView: View {
    @Environment(\.databaseContext) var databaseContext
    
    var body: some View {
        let value = try! databaseContext.reader.read { db in "Connected!" }
        Text(value)
    }
}

#Preview {
    LoaderView()
}

[Jason-Abbott]

@groue I think that should work perfectly. Thank you!

[groue]

Great! Please come back if something does not work as expected :-)