arrow-fx-coroutines / arrow.fx.coroutines / cancelBoundary

cancelBoundary

suspend fun ~~cancelBoundary~~(): Unit Deprecated: Use coroutineContext.ensureActive()

Inserts a cancellable boundary.

In a cancellable environment, we need to add mechanisms to react when cancellation is triggered. In a coroutine, a cancel boundary checks for the cancellation status; it does not allow the coroutine to keep executing in the case cancellation was triggered. It is useful, for example, to cancel the continuation of a loop, as shown in this code snippet:

import arrow.fx.coroutines.*

//sampleStart
suspend fun forever(): Unit {
  while(true) {
    println("I am getting dizzy...")
    cancelBoundary() // cancellable computation loop
  }
}

suspend fun main(): Unit {
  val fiber = ForkConnected {
    guaranteeCase({ forever() }) { exitCase ->
      println("forever finished with $exitCase")
    }
  }
  sleep(10.milliseconds)
  fiber.cancel()
}