`Channel`

inherits Object

A CSP-style channel for passing values between tasks. Channel.new is an unbuffered rendezvous -- a send parks until a receiver takes the value; Channel.buffered:n queues up to n values before sends park. close ends the conversation: further sends raise, receives drain the buffer then answer nil, and each: ends.

var ch = Channel.new;
Task.spawn:{ ch.send:42 };
ch.receive    "* -> 42

Class methods

buffered:Integer

A channel that buffers up to n values before sends park (0 is unbuffered).

var ch = Channel.buffered:2;
ch.send:1; ch.send:2; ch.close;
#( ch.receive ch.receive )    "* -> #(1 2)

native

new

An unbuffered (rendezvous) channel: every send waits for its receiver.

native

Instance methods

capacity

The buffer capacity; 0 for an unbuffered (rendezvous) channel.

native

Close the channel (idempotent); answers nil. Parked and future sends raise; buffered values remain receivable; a drained receive answers nil and each: ends.

native

closed?

True once the channel has been closed.

native

count

How many values are currently buffered (sent but not yet received).

native

each:Block

Run the block on each received value until the channel is closed and drained, parking between values; answers nil.

var ch = Channel.buffered:3;
ch.send:1; ch.send:2; ch.close;
var sum = 0;
ch.each:{ |v| sum = sum + v };
sum    "* -> 3

native

receive

The next value, parking until one is available -- buffered values first (FIFO), else directly from a parked sender. On a closed, drained channel answers nil.

native

send:

Send a value: hand it to a waiting receiver, else buffer it if there is room, else park until a receiver takes it. Raises on a closed channel. Answers nil.

native