Ruby Fiber.transfer用法及代码示例

transfer(args, ...) → obj

将控制权转移到另一根光纤，从上次停止的地方恢复它，如果之前没有恢复，则启动它。调用光纤将被暂停，就像调用 Fiber.yield 一样。

接收转接调用的光纤将其视为恢复调用。传递给 transfer 的参数被视为传递给 resume 的参数。

传入和传出光纤的两种控制方式(一种是 resume 和 Fiber::yield ，另一种是传入和传出光纤的 transfer )不能自由混合。

• 如果 Fiber 的生命周期从传输开始，它将永远无法让步或恢复控制传递，只能完成或传输回。 (它仍然可以恢复其他允许恢复的光纤。)

• 如果 Fiber 的生命周期从 resume 开始，它可以让出或转移到另一个 Fiber ，但只能以与它被放弃的方式兼容的方式接收控制权：如果它已经转移，它只能被转移返回，并且如果它已经屈服，它只能恢复返回。之后，它再次可以转移或屈服。

如果违反了这些规则，则会引发 FiberError 。

对于单独的 Fiber 设计，yield/resume更容易使用( Fiber 只是放弃控制权，不需要考虑控制权给谁)，而对于复杂的情况，传输更灵活，允许构建相互依赖的 Fibers 的任意图。

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