Signaling

NOTE: Signaling is a power user feature that can potentially lead to deadlocks if used improperly. Use at your own risk!

Signaling is an advanced technique similar to condition variables in typical multithreaded programming. One method within a concurrent object can suspend itself waiting for a particular event, allowing other methods to run. Another method can then signal all methods waiting for a particular event, and even send them a value in the process:

class SignalingExample
  include Celluloid
  attr_reader :signaled

  def initialize
    @signaled = false
  end

  def wait_for_signal
    value = wait :ponycopter
    @signaled = true
    value
  end

  def send_signal(value)
    signal :ponycopter, value
  end
end

The #wait_for_signal method in turn calls a method called "wait". Wait suspends the running method until another method of the same object calls the "signal" method with the same label.

The #send_signal method of this class does just that, signaling "ponycopter" with the given value. This value is returned from the original wait call.