example-supervision-01.kt

/*
 * Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
 */

// This file was automatically generated from exception-handling.md by Knit tool. Do not edit.
package kotlinx.coroutines.guide.exampleSupervision01

import kotlinx.coroutines.*

fun main() = runBlocking {
    val supervisor = SupervisorJob()
    with(CoroutineScope(coroutineContext + supervisor)) {
        // launch the first child -- its exception is ignored for this example (don't do this in practice!)
        val firstChild = launch(CoroutineExceptionHandler { _, _ ->  }) {
            println("First child is failing")
            throw AssertionError("First child is cancelled")
        }
        // launch the second child
        val secondChild = launch {
            firstChild.join()
            // Cancellation of the first child is not propagated to the second child
            println("First child is cancelled: ${firstChild.isCancelled}, but second one is still active")
            try {
                delay(Long.MAX_VALUE)
            } finally {
                // But cancellation of the supervisor is propagated
                println("Second child is cancelled because supervisor is cancelled")
            }
        }
        // wait until the first child fails & completes
        firstChild.join()
        println("Cancelling supervisor")
        supervisor.cancel()
        secondChild.join()
    }
}