interface SendChannel<in E>

Sender’s interface to Channel.



abstract val isClosedForSend: Boolean

Returns true if this channel was closed by invocation of close and thus the send and offer attempts throws exception.


abstract val isFull: Boolean

Returns true if the channel is full (out of capacity) and the send attempt will suspend. This function returns false for isClosedForSend channel.


abstract val onSend: SelectClause2<E, SendChannel<E>>

Clause for select expression of send suspending function that selects when the element that is specified as parameter is sent to the channel. When the clause is selected the reference to this channel is passed into the corresponding block.



abstract fun close(cause: Throwable? = null): Boolean

Closes this channel with an optional exceptional cause. This is an idempotent operation – repeated invocations of this function have no effect and return false. Conceptually, its sends a special “close token” over this channel.


abstract fun invokeOnClose(
    handler: (cause: Throwable?) -> Unit
): Unit

Registers handler which is synchronously invoked once the channel is closed or receiving side of this channel is cancelled. Only one handler can be attached to the channel during channel’s lifetime. Handler is invoked when isClosedForSend starts to return true. If channel is already closed, handler is invoked immediately.


abstract fun offer(element: E): Boolean

Adds element into this queue if it is possible to do so immediately without violating capacity restrictions and returns true. Otherwise, it returns false immediately or throws exception if the channel isClosedForSend (see close for details).


abstract suspend fun send(element: E): Unit

Adds element into to this channel, suspending the caller while this channel isFull, or throws exception if the channel isClosedForSend (see close for details).

Extension Functions


fun <E> SendChannel<E>.sendBlocking(element: E): Unit

Adds element into to this channel, blocking the caller while this channel Channel.isFull, or throws exception if the channel Channel.isClosedForSend (see Channel.close for details).



abstract class AbstractSendChannel<E> : SendChannel<E>

Abstract send channel. It is a base class for all send channel implementations.


interface BroadcastChannel<E> : SendChannel<E>

Broadcast channel is a non-blocking primitive for communication between the sender and multiple receivers that subscribe for the elements using openSubscription function and unsubscribe using ReceiveChannel.cancel function.


interface Channel<E> : SendChannel<E>, ReceiveChannel<E>

Channel is a non-blocking primitive for communication between sender using SendChannel and receiver using ReceiveChannel. Conceptually, a channel is similar to BlockingQueue, but it has suspending operations instead of blocking ones and it can be closed.


interface ProducerScope<in E> : 

Scope for produce coroutine builder.