Apple Media Library Access Permission retrieved programmatically - authorization

Question

I would appreciated some help please even if this is maybe a trivial question.
I've written a SwiftUI app that reads the media library from the device and plays it depending on user settings. That is all fine.
The problem I have is that if you install the app for the first time, the user needs to grant permission to access the media library. This appears to be a system generated dialog but I cannot see which step in the also triggers it. I tried to have the access request be triggered code generated but that doesn't seem to trigger the pop up but it still only appears at a later stage in the app load process. The code seems to recognise though that the user reacted to the access request pop up and does select the correct switch case.
What it does not seem to do though is that it still can't read the media library. The MPMediaQuery returns nil.
My suspicion is that it somehow connected to the fact that the access request doesn't run on the main thread but I am not experienced enough in Swift programming to know what the problem is. I would be most grateful for some helpful hints.
Here is my code:
import MediaPlayer
import SwiftUI
import Foundation
class Library {
var artists : [Artist] = []
#EnvironmentObject var settings : UserSettings
var counter : Float = 0
init() {
switch MPMediaLibrary.authorizationStatus() {
case .authorized:
print("authorized")
case .denied:
print("denied")
return
case .notDetermined:
print("not determined")
MPMediaLibrary.requestAuthorization() { granted in
if granted != .authorized {
return
}
}
case .restricted:
print("restricted")
#unknown default:
print("default")
}
if MPMediaLibrary.authorizationStatus() == .notDetermined { return }
let filter : Set<MPMediaPropertyPredicate> = [MPMediaPropertyPredicate(value: MPMediaType.music.rawValue, forProperty: MPMediaItemPropertyMediaType)]
let mediaQuery = MPMediaQuery(filterPredicates: filter )
var artistsInCollection : [Artist] = []
guard let _ = mediaQuery.items?.count else { return }
for item in mediaQuery.items! {
//here I do something but that's not relevant to my question
}
self.artists = artistsInCollection
}
}