class Channel(T)
inherits Reference

A Channel enables concurrent communication between fibers.

They allow communicating data between fibers without sharing memory and without having to worry about locks, semaphores or other special structures.

channel = Channel(Int32).new

spawn do
  channel.send(0)
  channel.send(1)
end

channel.receive # => 0
channel.receive # => 1

Note

Although a Channel(Nil) or any other nilable types like Channel(Int32?) are valid they are discouraged since from certain methods or constructs it receiving a nil as data will be indistinguishable from a closed channel.

Class methods

.receive_first(channels : Tuple | Array)

View source

.receive_first(*channels)

View source

.send_first(value, channels : Tuple | Array)

View source

.send_first(value, *channels)

View source

.new(capacity = 0)

View source

Methods

#close : Bool

Closes the channel. The method prevents any new value from being sent to / received from the channel. All fibers blocked in send or receive will be awakened with Channel::ClosedError

Both awaiting and subsequent calls to #send will consider the channel closed. All items successfully sent to the channel can be received, before #receive considers the channel closed. Calling #close on a closed channel does not have any effect.

It returns true when the channel was successfully closed, or false if it was already closed.

View source

#closed?

View source

#inspect(io : IO) : Nil

Appends a String representation of this object which includes its class name, its object address and the values of all instance variables.

class Person
  def initialize(@name : String, @age : Int32)
  end
end

Person.new("John", 32).inspect # => #<Person:0x10fd31f20 @name="John", @age=32>

View source

#pretty_print(pp)

View source

#receive : T

Receives a value from the channel. If there is a value waiting, then it is returned immediately. Otherwise, this method blocks until a value is sent to the channel.

Raises ClosedError if the channel is closed or closes while waiting for receive.

channel = Channel(Int32).new
spawn do
  channel.send(1)
end
channel.receive # => 1

View source

#receive? : T?

Receives a value from the channel. If there is a value waiting, it is returned immediately. Otherwise, this method blocks until a value is sent to the channel.

Returns nil if the channel is closed or closes while waiting for receive.

View source

#send(value : T)

Sends a value to the channel. If the channel has spare capacity, then the method returns immediately. Otherwise, this method blocks the calling fiber until another fiber calls #receive on the channel.

Raises ClosedError if the channel is closed or closes while waiting on a full channel.

View source