Ruby Fiber.transfer用法及代碼示例

transfer(args, ...) → obj

將控製權轉移到另一根光纖，從上次停止的地方恢複它，如果之前沒有恢複，則啟動它。調用光纖將被暫停，就像調用 Fiber.yield 一樣。

接收轉接調用的光纖將其視為恢複調用。傳遞給 transfer 的參數被視為傳遞給 resume 的參數。

傳入和傳出光纖的兩種控製方式(一種是 resume 和 Fiber::yield ，另一種是傳入和傳出光纖的 transfer )不能自由混合。

• 如果 Fiber 的生命周期從傳輸開始，它將永遠無法讓步或恢複控製傳遞，隻能完成或傳輸回。 (它仍然可以恢複其他允許恢複的光纖。)

• 如果 Fiber 的生命周期從 resume 開始，它可以讓出或轉移到另一個 Fiber ，但隻能以與它被放棄的方式兼容的方式接收控製權：如果它已經轉移，它隻能被轉移返回，並且如果它已經屈服，它隻能恢複返回。之後，它再次可以轉移或屈服。

如果違反了這些規則，則會引發 FiberError 。

對於單獨的 Fiber 設計，yield/resume更容易使用( Fiber 隻是放棄控製權，不需要考慮控製權給誰)，而對於複雜的情況，傳輸更靈活，允許構建相互依賴的 Fibers 的任意圖。

例子：

manager = nil # For local var to be visible inside worker block

# This fiber would be started with transfer
# It can't yield, and can't be resumed
worker = Fiber.new { |work|
  puts "Worker: starts"
  puts "Worker: Performed #{work.inspect}, transferring back"
  # Fiber.yield     # this would raise FiberError: attempt to yield on a not resumed fiber
  # manager.resume  # this would raise FiberError: attempt to resume a resumed fiber (double resume)
  manager.transfer(work.capitalize)
}

# This fiber would be started with resume
# It can yield or transfer, and can be transferred
# back or resumed
manager = Fiber.new {
  puts "Manager: starts"
  puts "Manager: transferring 'something' to worker"
  result = worker.transfer('something')
  puts "Manager: worker returned #{result.inspect}"
  # worker.resume    # this would raise FiberError: attempt to resume a transferring fiber
  Fiber.yield        # this is OK, the fiber transferred from and to, now it can yield
  puts "Manager: finished"
}

puts "Starting the manager"
manager.resume
puts "Resuming the manager"
# manager.transfer  # this would raise FiberError: attempt to transfer to a yielding fiber
manager.resume

produces

Starting the manager
Manager: starts
Manager: transferring 'something' to worker
Worker: starts
Worker: Performed "something", transferring back
Manager: worker returned "Something"
Resuming the manager
Manager: finished