Block yielding to a block, via fibers.

fibers_with_blocks.rb

# importer/exporter interaction via fibers

require 'fiber'

class Importer
  DATA = [
    ["foo", "bar"],
    ["jazz", "quux"],
    ["cats", "dogs"]
  ]

  def initialize
    @data = DATA.dup.each
  end

  def import
    loop do
      yield(@data.next)
    end
  end
end

class Exporter
  def export
    loop do
      value = yield
      puts "exporting: #{value}"
    end
  end
end

importer = Importer.new
exporter = Exporter.new

fiber = Fiber.new do
  importer.import { |v| Fiber.yield(v) }
  raise StopIteration
end

exporter.export { fiber.resume }