class

Channel(T)

Inherits Iterator / Enumerable / Reference / Object

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.

Constructors

new(capacity : Int32 = 0)

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Class methods

receive_first(channels : Enumerable(Channel))

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receive_first(*channels)

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send_first(value, channels : Enumerable(Channel)) : Nil

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send_first(value, *channels) : Nil

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Instance methods

Closes the channel. The method prevents any new value from being sent to the channel.

If the channel has buffered values, then subsequent calls to receive will succeed and consume the buffer until it is empty.

All fibers blocked in send or receive will be awakened with Channel::ClosedError. All subsequent calls to #send will consider the channel closed. Subsequent calls to #receive will consider the channel closed if the buffer is empty.

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.

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closed?

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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>

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Returns the next element in this iterator, or Iterator::Stop::INSTANCE if there are no more elements.

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pretty_print(pp)

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receive

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

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receive?

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.

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send(value : T) : self

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.

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Nested types

Channel::ClosedError