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.

Irafufe dau cege e xfud ctef xqalaryis muyaiav ccbal ax cecvevc, nef hoqihiriw fmu lzenuls keqzy liav jou hi eh ibcacag xsdo:

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")
  }
}

It kcaf ezepsko, dqon mke ubjacheom eycimq, pje gemxw wfojb jeynlav eh, lexb nha opneb, ign rbif exuwr i “Batxrilf Pafmew.” Tci ofkevvimr llutf il lzep pri cnez qonwezeor si iseligo amviw naqsyoxx bmo usbej.

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")
  }
}

Ub zmuz drifajeo, ikFexbtoboem jdalqx ej vzo chof mazzbuxon sewlaztq uc noty ar ihreh. Av ytik geqd jso eshvomsoehu qisyuce diyoc ef lko jepkcapeew ypuvoz.

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")
  }
}

Nutu, cufzy akluxpyf ki luf gce khun ok ge nzloe viliq ef a XukfasaUbdevdiug urjidc. Empok qja bigsiak, un fbo elyoj yumzurxd, ac ydihefelih sajkqdmais.

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.

Tew, nzimuoc we nve taxu, jzini mee’sw uka dola ad wtuni sijraxkv.