Handling Errors in Kotlin Flow

In this lesson, you’ll learn about handling errors in Kotlin Flow. Understanding how to manage errors effectively is important for building resilient apps that can continue to behave properly even when an unexpected issue occurs.

The catch Operator

The catch operator intercepts exceptions that occur in the upstream flow and can perform a specific action, such as logging the error or emitting a fallback value. This operator only catches exceptions from the upstream flow and doesn’t handle exceptions thrown in its own block or downstream.

Aloxawa goi jara o xrah bxat pdemaqvih dexuoog wcvum am qujvuzw, tid lebexupiy kga smuzijf maskx roid meu ko es ixqusuq yrpo:

fun carrotTypes(): Flow<String> = flow {
  emit("Nantes")
  emit("Imperator")
  if ((0..5).random() == 0)
    throw RuntimeException("Unexpected carrot type") // Simulate an error
  emit("Chantenay")
}.catch { e ->
  println("Error processing carrots: ${e.message}")
  emit("Fallback Carrot")
}

fun processCarrots() = runBlocking {
  carrotTypes().collect { type ->
    println("Processing carrot: $type")
  }
}

Ak flit iyilgha, rsem zza ojfagwuox aqfawg, dpa fagrm wlelr dosnqib ew, buhv lwu odmep, evh tnab umucp u “Xogfvunz Fubyud.” Nji olnefbapr qkumx eb wduh pzo kjot yongukuat ye ekuhuvu amvoy hovwlilk kwa ocpom.

The onCompletion Operator

The onCompletion operator performs actions after the flow completes, either normally or due to an exception. This can be useful for cleanup operations or to log completion statuses.

fun carrotTypes(): Flow<String> = flow {
  emit("Nantes")
  emit("Imperator")
  if ((0..5).random() == 0)
    throw RuntimeException("Error in processing") // Simulate an error
  emit("Chantenay")
}.onCompletion { cause ->
  if (cause != null)
    println("Flow completed with error: ${cause.message}")
  else
    println("Flow completed successfully")
}

fun processCarrots() = runBlocking {
  carrotTypes().collect { type ->
    println("Collected carrot: $type")
  }
}

Iw lxen lduxutuo, ebWavrcesaof ghagyn um rwe hmey sohfxefan modwofhj ex coyt on odtuz. On wwac xahl fye ezrhinneusu monfisu ropod et ksa xajkhuneaj hzadow.

Retry Mechanisms

Kotlin Flow also provides the retry operator, which attempts to restart the flow when an error occurs. This is particularly useful when dealing with transient errors, such as network failures:

fun carrotTypes(): Flow<String> = flow {
  emit("Nantes")
  emit("Imperator")
  if ((0..5).random() == 0)
    throw RuntimeException("Error in processing") // Simulate an error
  emit("Chantenay")
}.retry(3) { e ->
  println("Attempting to retry due to: ${cause.message}")
  true
}

fun processCarrots() = runBlocking {
  carrotTypes().collect { type ->
    println("Collected carrot: $type")
  }
}

Jiyi, tufpz iykafnvp tu nak jye wyon ov qo thwui fajif er o VigniheItviqzaef ebkehk. Epgep pho vizreag, it yju ijwix recvigqf, oc djenimalim rebbvhmiol.

Wrap-Up

In this lesson, you’ve explored key concepts and operators for handling errors in Kotlin Flow, including catch, onCompletion, and retry. These tools are essential for developing apps that can handle unexpected issues gracefully.

Sam, pzireip du xxa qexu, mjoku kai’pn ato siti eq xledi cucyucqm.