AllAbout 019 Fiber

fib.rb

fibonacci = Fiber.new do
  x, y = 0, 1
  loop do
    Fiber.yield y # yieldに渡した値がresumeの返り値となる
    x, y = y, x + y
  end
end

puts fibonacci.resume #=> 1
puts fibonacci.resume #=> 1
puts fibonacci.resume #=> 2
puts fibonacci.resume #=> 3
puts fibonacci.resume #=> 5
puts fibonacci.resume #=> 8
puts fibonacci.resume #=> 13

new.rb

Fiber.new
# => ArgumentError: tried to create Proc object without a block

f = Fiber.new { puts 'fiber!' }
#=> #<Fiber:0x007f9175d7d210>

Fiber.ancestors
# => [Fiber, Object, Kernel, BasicObject]

Fiber.instance_methods(false)
#=> [:resume]

f.resume
# => fiber!

no_transfer.rb

# transferを使わない
f1 = Fiber.new { 'one' }
f2 = Fiber.new { f1.resume; 'two' }

puts f2.resume #=> two

# f1もf2も既に死んでいる
puts f1.resume #=> dead fiber called (FiberError)
puts f2.resume #=> dead fiber called (FiberError)

proc.rb

pr = Proc.new { puts 'proc!' }
pr.call # => proc!

resume.rb

f = Fiber.new do
  Fiber.yield 'return by yield' # 処理を親に戻す
  Fiber.yield 'return by yield again'
  'end of block'
end

puts '--- 1 ---'
f.resume #=> 'return by yield'
puts '--- 2 ---'
f.resume #=> 'return by yield again'
puts '--- 3 ---'
f.resume #=> 'end of block'
puts '--- 4 ---'
f.resume #=> FiberError: dead fiber called

transfer.rb

# transferを使う
require 'fiber'

f1 = Fiber.new { 'one' }
f2 = Fiber.new { f1.transfer; 'two' }

puts f2.resume #=> one

# 一度transferしたfiberはresumeできない
puts f1.resume #=> cannot resume transferred Fiber (FiberError)
puts f2.resume #=> double resume (FiberError)