Connection error when running on Mac in ‘Designed for iPad’ mode

[matiaskorhonen]

I get a The operation couldn’t be completed. (GRDBQuery.DatabaseContextError error 0.) (aka DatabaseContextError.notConnected) error when trying to run my iPad app on an Apple Silicon Mac in iPad compatibility mode.

The same app works when run in the Simulator and on iPhones so I'm not sure what's going on here. Is there some additional debug output that I could enable to see why the connection isn't working?

The database context setup would appear to work just fine, or at least I can dump the schema. The error only appears in the view where I have a @Query.

import GRDB
import GRDBQuery
import SwiftUI

@main
struct RedactedApp: App {
    var body: some Scene {
        WindowGroup {
            AppView()
        }.databaseContext(.readOnly {
            let dbURL = Bundle.main.path(forResource: "database", ofType: "sqlite3")!
            var config = Configuration()
            config.readonly = true
            let dbQueue = try DatabaseQueue.inMemoryCopy(fromPath: dbURL, configuration: config)

            try dbQueue.dumpSchema() // <-- Just for debugging. The schema dump is shown in
                                     //  the logs so the connection would appear to be working

            return dbQueue
        })
    }
}

Versions:

• GRDB.swift: 7.3.0
• GRDBQuery: 0.10.1
• macOS: Sequoia 15.3.1
• Xcode: 16.2

[groue]

hello @matiaskorhonen,

The database context setup would appear to work just fine, or at least I can dump the schema.

Thanks for checking that. You can dump the schema when you create the context, and this means that the connection is well established.

Now, DatabaseContextError.notConnected is not an error thrown from an established connection. It is an error thrown from a missing connection.

It looks like the database context present in the environment is not connected - it is likely the default database context, not the one you have configured. 🤔

I admit I lack experience about Mac apps in iPad compatibility mode. Could it be that the SwiftUI environment behaves differently?

I would place this view somewhere in the app in order to test if the database context is connected:

struct DatabaseConnectionTestView: View {
    @Environment(\.databaseContext) var databaseContext

    var body: some View {
        Text(databaseValue())
    }
     
    private func databaseValue() -> String {
        do {
            return try databaseContext.reader.read { _ in "Success" }
        } catch {
            return String(describing: error)
        }
    }
}

For example, I expect this app to display "Success". When I run it on my Mac (Sonoma 14.5, I'm late), in iPad compatibility mode, from with Xcode 16.2, it does:

@main
struct RedactedApp: App {
    var body: some Scene {
        WindowGroup {
            DatabaseConnectionTestView()
                .databaseContext(.readOnly { try DatabaseQueue() })
        }
    }
}

[matiaskorhonen]

It looks like something weird happens with sheets and full-screen covers in the iPad compatibility mode.

I added what you suggested to the view where I'm having issues, and it reports ‘Success’ despite the queries still failing.

I even tested out checking that the DB can be queried by checking if a table exists†, and that worked too.

If I render the same view right in the NavigationSplitView that's at the root of my app, then it works again, but if it's presented via a .sheet or .fullScreenCover, then the queries fail, but only when running on the Mac in iPad mode.

Super bizarre, I expected that this should all work just like it does on an iPad, but obviously something very weird is happening somewhere, possibly inside Apple's code.

---

† table exists code:

private func databaseValue() -> String {
    do {
        return try databaseContext.reader.read { db in
            return try db.tableExists("my_table") ? "Table exists" : "Doesn't exist"
        }
    } catch {
        return String(describing: error)
    }
}

[groue]

It looks like something weird happens with sheets and full-screen covers in the iPad compatibility mode.

This reminds me of early SwiftUI, where sheets would not inherit environment values.

Did you try to re-inject the environment in sheets?

 struct MyView: View {
+  @Environment(\.databaseContext) var databaseContext
   var body: some View {
     ContentView().sheet(...) {
       MySheet()
+        .databaseContext(databaseContext)
     }
   }
 }

If this works, it would be a good idea to submit a feedback to Apple.

I added what you suggested to the view where I'm having issues, and it reports ‘Success’ despite the queries still failing.

This does not make sense, unless the queries feed somewhere else. Maybe you are using a custom database context?

[matiaskorhonen]

Did you try to re-inject the environment in sheets?

Yeah, re-injecting the database context seems to have worked! Despite it already being supposedly present 😑. Looks like an Apple bug.

Maybe you are using a custom database context?

I'm not. My database context is pretty close to the simplified version I posted in my first message. I even tried simplifying it to the bare minimum and that didn't seem to have any effect.

[groue]

Great! Happy we found a solution. It definitely looks like a bug indeed. Fortunately, when Apple fixes it, the workaround should not introduce any problem!

And hello to Helsinki, a city I was happy to visit a few years ago 👋