CompletionHandler

typealias CompletionHandler = (cause: Throwable?) -> Unit(source)

Handler for Job.invokeOnCompletion and CancellableContinuation.invokeOnCancellation.

Installed handler should not throw any exceptions. If it does, they will get caught, wrapped into CompletionHandlerException, and rethrown, potentially causing crash of unrelated code.

The meaning of cause that is passed to the handler:

  • Cause is null when the job has completed normally.

  • Cause is an instance of CancellationException when the job was cancelled normally. It should not be treated as an error. In particular, it should not be reported to error logs.

  • Otherwise, the job had failed.

Note: This type is a part of internal machinery that supports parent-child hierarchies and allows for implementation of suspending functions that wait on the Job's state. This type should not be used in general application code. Implementations of CompletionHandler must be fast and lock-free.