I'm retrieving a list of documentSnapshot from Fir...

# announcements

[Ale]

I'm retrieving a list of documentSnapshot from Firestore, coverted to POJOs:

private fun extractLevels(querySnapshot: QuerySnapshot): List<Level?> {
    return querySnapshot.documents
        .map { it.toObject(Level::class.java) }
}

If the list of documents is empty, this should just return an empty list, right? There shouldn't be nulls in the list. However, unless I set the return type as List<Level?>), I get an error because it's actually expecting that. What am I doing wrong, and how can I have this return a List<Level> ?

[Tobias Berger]

probably toObject returns something nullable, so the resulting map could (from a compiler POV) contain null values

[Tobias Berger]

if you want to handle that case, you can do so in the map-lambda. If you are sure that null is impossible, you could do !! after the toObject call, but I personally find this to be a bad practice.
If nulls aren't an issue here, you can just replace map witch mapNotNull. That will check each mapping result and just exclude nulls from the resulting list, which then also has the non-null generic type.

[Ale]

ah, brilliant, thank you!