broadcast.rb

class Broadcaster
  attr_reader :ractor
  def initialize
    @ractor = new_ractor
  end
  def new_ractor
    Ractor.new { Ractor.recv rescue nil }
  end
  def broadcast(message)
    next_ractor = new_ractor
    @ractor.define_singleton_method(:next) { next_ractor }
    frozen_message = message.dup.freeze
    @ractor.define_singleton_method(:message) { frozen_message }
    @ractor.close
    @ractor = next_ractor
  end

  class Receiver
    def initialize(ractor)
      @ractor = ractor
    end
    def recv
      @ractor.take rescue nil
      message = @ractor.message
      @ractor = @ractor.next
      message
    end
  end
end

bc = Broadcaster.new
4.times do |i|
  Ractor.new i, bc.ractor do |i, r|
    rec = Broadcaster::Receiver.new r
    loop do
      message = rec.recv
      puts "ractor#{i} received #{message}"
    end
  end
end

(1..).each do |i|
  bc.broadcast "hello#{i}"
  sleep 1
end

__END__
ractor0 received hello1
ractor1 received hello1
ractor2 received hello1
ractor3 received hello1
ractor3 received hello2
ractor1 received hello2
ractor0 received hello2
ractor2 received hello2
ractor1 received hello3
ractor2 received hello3
ractor0 received hello3
ractor3 received hello3
...