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callbackFlow with Firebase — convert RealtimeDatabase callbacks to callbackFlow | by Saqib | April 2023

photograph taken by Luis Tosta ABOVE depart

Content material

  • overview Move And channelFlow
  • callbackFlow featured
  • Why/When to make use of callbackFlow ?
  • callbackFlow Below the hood
  • Firebase Setup and Dependencies — (this step is simply in case if you wish to attempt Firebase realtime database your self utilizing the offered github venture, In any other case you possibly can skip this step and transfer on to the subsequent one)
  • firebase RealtimeDatabase name again
  • convert RealtimeDatabase name again callbackFlow
  • How you can accumulate callbackFlow ?
  • Github venture

Overview of Move and channelFlow

  • Move is the underlying stream of information emitted then collected and many others in sequence. After lambda play is full Move would not emit any extra worth and it is closed
  • channelFlow just like Move however with a buffer and buffer measurement of 64, it permits a number of values ​​to be emitted earlier than every emitted worth is collected. It additionally behaves in the identical method as Move in its default utilization i.e. it stops emitting values ​​after going out of the scope of the lambda, however in channelFlow we are able to nonetheless cease closing lambda utilizing awaitClose api inside lambda and ship following worth with predefined methodology. However this isn’t best selection for circumstances the place we need to accumulate information from any callback holding Move alive and might ship information later.

callbackFlow Options

Why/When to make use of callbackFlow?

  • Learn community standing on system — (take a number of photographs)
  • Learn system location information — (a number of seize)
  • Deal with any Third Occasion library callbacks which can be offering real-time information e.g. Firebase callbacks – (a number of occasions)

callbackFlow UnderTheHood

public enjoyable <T> callbackFlow(@BuilderInference block: droop ProducerScope<T>.() -> Unit): Move<T> = CallbackFlowBuilder(block)
  1. callbackFlow use CallbackFlowBuilder class to create
  2. CallbackFlowBuilder class is overriding ChannelFlowBuildermeaning it is constructed on channelFlow .
  3. callbackFlow request for offering awaitClose inside block to verify the stream continues to be lively and might unregister the inside listener awaitClose code block to verify callbackFlow unregister the listener when it’s canceled/closed in any other case the listener might leak.
  4. callbackFlow will elevate IllegalStateException if we is not going to ship awaitClose so it ensures awaitClose Existence block just isn’t like channelFlow.

Firebase Setup and Dependencies

  1. go to Firebase Dashboard and Create a Firebase venture
  2. Register your Android app with Firebase venture utilizing instruct.
  3. After registering your Android app with the Firebase venture, it is possible for you to to obtain the configuration file google-services.json Add that file to your application-level root listing
  4. To allow Google providers, add the next Google providers plugin root-level construct.gradle file as construct script dependency

Firebase Realtime Database Callback

convert RealtimeDatabase name again callbackFlow

implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.0-RC'
  • Use a return perform like Move<String> .
  • callbackFlow the return block, the inside block creates the database reference and subscribes it to the database reference to hear for updates within the callbacks.
  • trySend(worth?.toString().orEmpty()) inside assertion onDataChange the callback will ship the worth to the collector callbackFlow .
  • awaitClose get a block of code to unregister the occasion listener when callbackFlow Canceled.

How you can accumulate callbackFlow?


Github venture

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Updated: April 26, 2023 — 11:31 pm

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