lucasvalenteds / firebase-android-coroutines

Async/Await support for Firebase Android SDK

Deprecation notice

A better implementation has been merged into the official kotlin/kotlinx.coroutines repository.

Please, use the official implementation instead.

Module kotlinx-coroutines-firebase

Integration with Firebase Task and DatabaseReference for Android.

Extension functions:

Name	Description
Task.await	Awaits for completion of the Task and return the result
DatabaseReference.readValue	Awaits for a single value to be retrieved from Firebase Database
DatabaseReference.readList	Awaits for a List of values to be retrieved from Firebase Database

Example

Working with Firebase Authentication

The following code shows how to get an user from Firebase and delete it using two approaches.

The standard approach is to write nested callback functions.

val auth = FirebaseAuth.getInstance()

auth.getUserByEmail(email)
    .addOnSuccessListener { user ->
        auth.deleteUser(user.uid)
            .addOnSuccesListener { println("User deleted") }
            .addOnFailureListener { exception -> println(exception) }
    }
    .addOnFailureListener { exception -> println(exception) }

The other approach is the use of a suspended coroutine to make the code flatter, so we can call the await() method to wait the first asyncronous operations (retrieve the user) to complete before starting the second one (delete the user).

val auth = FirebaseAuth.getInstance()

try {
  val user = auth.getUserByEmail(email).await()

  auth.deleteUser(user.uid).await()

  println("User deleted")
} catch (exception: FirebaseAuthException) {
  println(exception)
}

Working with Firebase Database

Another usage of this module is to access nodes from a Firebase Database instance.

There are two suspend functions that encapsulate callbacks: readValue and readList.

The usage of both methods can be seen in the code below. It shows how to read a a single value using readValue to read the player name and readList function to read his/her last five points in the game.

val database = FirebaseDatabase.getInstance()
val gameNode = database.getReference("game")
 
val person = gameNode.child("player").readValue<String>()
val scores = gameNode.child("scores").readList<Int>()
 
println("Scores of $person")
scores.forEach(::println)

It's important to mention that since this modules exposes coroutines, they must be run inside a context like launch {}, async {} or runBlocking for testing purpose.

Test results

Package kotlinx.coroutines.firebase.android

Integration with Firebase Task and DatabaseReference for Android.