example of using _createMoorIsolate

[matthewkooshad]

from https://moor.simonbinder.eu/docs/advanced-features/isolates/,
i'm not using VmDatabase.memory(), but rather an on-disk db, since i need the data to persist when the flutter app is closed.

from https://moor.simonbinder.eu/docs/advanced-features/isolates/#initialization-on-the-main-thread,
i see Future _createMoorIsolate() async , but i don't see an example of calling this. could i see an example of calling this?

in my main method, i started to put the line below there to set a global Database db variable for me to use this isolate db, but i need to see how to use this with _createMoorIsolate.
Future main() async {
db = Database.connect(DatabaseConnection.delayed(_connectAsync()));

as i noticed _connectAsync from that doc returns a Future
but, _createMoorIsolate from that doc returns a Future

[simolus3]

DatabaseConnection.delayed is the way to go. It takes a future as an argument and returns a connection that is ready once the future completes.
So you should be able to just setup the database like this:

void main() {
  db = Database.connect(DatabaseConnection.delayed(_createMoorIsolate()));
  // ...
}

as i noticed _connectAsync from that doc returns a Future
but, _createMoorIsolate from that doc returns a Future

I don't see a contradiction here :D If you want to turn a Future<DatabaseConnection> into a DatabaseConnection, use DatabaseConnection.delayed.
If that doesn't work for you please let me know.

[simolus3]

Ah sorry, I think the problem is that you're creating the database before the messenger has been initialized. Try calling WidgetsFlutterBinding.ensureInitialized at the start of your main method.

Btw, you can make initDatabase async and use

Future<void> initDatabase() async {
  final isolate = await _createMoorIsolate();
  final connection = await isolate.connect();
  db = Database.connect(connection);
}   

Then, just await initDatabase in main since you're in an async context already.

[matthewkooshad]

thanks, after doing those 2 things, i now see on the call stack both: main and _startBackground simultaneously running!

also, my existing db methods appear working the same as before.

[matthewkooshad]

i also checked by removing WidgetsFlutterBinding.ensureInitialized from the start of my main method, and the problem with getApplicationDocumentsPath shows again just as before.

i read a bit here about this snippet:
https://stackoverflow.com/questions/63873338/what-does-widgetsflutterbinding-ensureinitialized-do/63873689
but, it's not clear to me, if this is a hack(?) that would be fine for production version or if i should be looking into another way to getApplicationDocumentsPath.. -- thoughts? thanks

[simolus3]

getApplicationDocumentsPath works by sending a platform message to native code. By default, Flutter only initializes the native messenger after runApp was called. If you want to use that messenger before you call runApp, you need to call the ensureInitialized method or you get the exception you've seen. There's nothing wrong with that approach IMO, it's a valid solution that works. I wouldn't call it a hack.

[matthewkooshad]

thanks much for explaining this further; I'm glad to get this working! thank you