When to add scheduling option .immediate?

[Jasperav]

This is from the documentation:

The scheduling: .immediate option should be removed for database requests that are too slow.

Does this apply to a network request, or just a slow query? I want to show a spinner when a user sees my screen, because I am doing a network request to populate my database. After that, I want to show the list.

Which scheduling option should I use in the case of a network request?

[groue]

The scheduling: .immediate option only applies to ValueObservation (documentation). It has the database observation publisher publish its first element immediately, right on subscription.

The publisher is subscribed when a view that contains a @Query property enters the screen, when requested by SwiftUI, from the main thread. When this publisher is .immediate, this allows the view to display database value right from the start (with multiple benefits: see Why @Query?).

But when the database request is slow, this will block the main thread until the ValueObservation has performed its initial fetch. The user may see a noticeable delay before the view appears on screen, and the app won't be responsive.

That's why "database requests that are too slow" should not use the scheduling: .immediate option. Without this option, the initial fetch will happen in the background, and the main thread will not be blocked. But the view will have to display something until the fetch completes, and that something is the default value of the Queryable type.

Does this apply to a network request, or just a slow query? I want to show a spinner when a user sees my screen, because I am doing a network request to populate my database. After that, I want to show the list.

If your Queryable type returns a publisher that can't publish anything until a network request has completed, then you can use the defaultValue in order to tell your view to display the spinner. And if the publisher starts observing the database after the network request has completed, then do not use the .immediate option, since you do not need it.

[Jasperav]

Alright thanks I got it, I will use the async(onQueue) display a spinner while the network request is going on

[groue]

Yes! Mind async(onQueue: .main) is the default (you don't have to specify anything).