Channel is the Kotlin approach for handling a "hot stream" of items, where the work to build the items starts immediately, irrespective of whether anyone is around to consume the results.

A simple way to create a Channel is to use the produce() function on CoroutineScope. You provide a lambda expression, and it calls send() for every item that should be placed into the stream. Here, we send a series of random numbers, with a delay between each. Since produce() is defined on CoroutineScope, though, we need to either:

  • Call produce() from directly inside of our launch() coroutine builder (as this is a CoroutineScope in that lambda expression), or

  • Define our function that uses produce() (randomPercentages()) as an extension function on CoroutineScope

A simple way to consume a Channel is to call consumeEach(). This takes a lambda expression, and it is passed each send item from the Channel. consumeEach() is a suspend function, so we need to call consumeEach() from inside of another suspend function or from a coroutine builder, such as launch().

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A Conflated Channel A Fixed-Buffer Channel A Simple Channel A Zero-Buffer Channel BroadcastChannel Channel and receive() Channels and Fan-out Hot Channels Via offer() The Channel() Function toList() for Channel
A Conflated Channel A Fixed-Buffer Channel A Parallel Coroutine Sample A Sequential Coroutine Sample A Simple Channel A Simple Coroutine Sample A Simple Flow A Simple SharedFlow A Simple StateFlow A Zero-Buffer Channel async() BroadcastChannel cancelAndJoin() Canceling a Job Canceling a Parent Cancels Its Children Canceling and Cooperation catch() Channel and receive() Channels and Fan-out combine() Operator Contexts and Jobs Cooperation by Checking isActive Cooperation by Yielding debounce() Operator distinctUntilChanged() Operator distinctUntilChangedBy() Operator drop() Operator dropWhile() Operator filter() Operator filterIsInstance() Operator filterNot() Operator filterNotNull() Operator first() and Flow flattenConcat() Operator flattenMerge() Operator Flow Actions Flow onStart() flowOf() flowOn() Flows and Exceptions fold() Operator Hot Channels Via offer() invokeOnCompletion() Jobs and Parents Jobs Cancel When They Crash join() Lazy Coroutines map() Operator mapLatest() Operator mapNotNull() Operator Massively Parallel Coroutines MutableSharedFlow Replay Option Non-Cancellable Coroutines Parent Jobs Cancel When a Child Crashes promise() retry() retryWhen() runBlocking() sample() Operator scan() Operator single() and singleOrNull() Starting Lazy Coroutines StateFlow and Content Equality suspend Functions and Flows Suspending main() take() Operator takeWhile() Operator The Channel() Function TimeoutCancellationException Timeouts toList() and toSet() toList() for Channel withIndex() Operator withTimeoutOrNull() zip() Operator
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