How to create a coroutine Dispatcher for the current thread?

user_842697 0
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Is it possible to create a Dispatcher for the current thread? Check this sample code as an example of what I want to accomplish:

val dispatcher = if (parallel) {
  Dispatcher.Default
} else {
  // What should I write here so I just use the current thread to run doStuff?
}

val deferredList = list.map {
  async(dispatcher) { doStuff(it) }
}
kotlin-coroutines kotlin multithreading
2 Answers

When you build a coroutine, you're passing a CoroutineContext as argument. If you don't pass anything, the new coroutine is built with the current CoroutineContext (its parent's context).

Instead of a Dispatcher you should aim to a CoroutineContext:

val context = if (parallel) {
    Dispatchers.Default
} else {
    coroutineContext
}

val deferredList = list.map {
    async(context) { doStuff(it) }
}

You can also "extract" every Element of the context individually using the Element type as key:

Job: coroutineContext[Job]

Dispatcher: coroutineContext[ContinuationInterceptor]

ExceptionHandler: coroutineContext[CoroutineExceptionHandler]

Name: coroutineContext[CoroutineName]

user_90195760

Use Dispatchers.Unconfined, it's used exactly to run on a current thread.

The whole code will look as follows:

val dispatcher = if (parallel) Dispatcher.Default else Dispatchers.Unconfined

val deferredList = list.map {
  async(dispatcher) { doStuff(it) }
}
user_43372430
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