I m trying to de dupelicate some Flow code I basically have this method repeated pretty much identically for a bunch of different firestore queries Is there a way to wrap this up so I don t have to do all of this cermoney for each firestore query I write ```fun getBooks Flow lt List lt Book gt gt return callbackFlow val listener = FirebaseFirestore getInstance collection books addSnapshotListener value error gt trySend value to error awaitClose listener remove doSomethingWithNullValueAndError conflate map value gt value toObjects flowOn defaultDispatcher ```

I'm trying to de-dupelicate some Flow code. I basically have this method repeated pretty much identically for a bunch of different firestore queries. Is there a way to wrap this up so I don't have to do all of this cermoney for each firestore query I write?

fun getBooks(): Flow<List<Book>> {
  return callbackFlow {
    val listener =
      FirebaseFirestore.getInstance().collection("books").addSnapshotListener { value, error -> trySend(value to error) }
    awaitClose { listener.remove() }
  }
  .doSomethingWithNullValueAndError()
  .conflate()
  .map { (value, _) -> 
    value.toObjects()
  }
  .flowOn(defaultDispatcher)

In an ideal api (i think) i'd be able to write something like this

fun getBooks(): Flow<List<Book>> {
val query = FirebaseFirestore.getInstance().collection("books")
return getFirestoreFlowable(query, Book.class::java)
}

and

fun getPeople(): Flow<List<Person>> {
val query = FirebaseFirestore.getInstance().collection("person").        .whereEqualTo("person.visibility", true)
return getFirestoreFlowable(query, Person.class::java)
}

and then I'd have a generic

fun <T> getFirestoreFlowable(query: Query, type: T): Flow<T> {
  return callbackFlow {
    val listener =
      query.addSnapshotListener { value, error -> trySend(value to error) }
    awaitClose { listener.remove() }
  }
  .doSomethingWithNullValueAndError()
  .conflate()
  .map { (value, _) -> 
    value.toObjects()
  }
  .flowOn(defaultDispatcher)

Does that sound or look alright?

Joffrey

08/07/2022, 2:48 PM

What is

doSomethingWithNullValueAndError()

? If you're throwing on errors, why not just do it with the

close(Throwable)

from inside the

callbackFlow

? Also, I'd rather declare such functions as extensions, for instance an extension function on

Query

here

Another question, where do you use

type

here?

Colton Idle

08/07/2022, 5:35 PM

I just got

doSomethingWithNullValueAndError()

from a snippet that @uli was helping me with. An exntention function on query makes sense here to me. Where do I use type... Hm. I need it for the

value.toObjects()

so that it knows what type to return

2 Views

#getting-started Join Slack