ruby - How can Enumerator stop in the middle of method execution? -

(example ruby tapas episode. 59)

@names = %w[ylva brighid shifra yesamin]  def names   yield @names.shift   yield @names.shift   yield @names.shift   yield @names.shift end  enum = to_enum(:names) enum.next # => ylva @names    # => ["brighid", "shifra", "yesamin"] 

names method execution seems stop after first line. if names executed entirely, @names should become empty. how can magic (= calling method partially) happen?

it working expected. on invocation enum.next calls first line in names method , yields caller, i.e. stops flow of execution of names method @ point. on next invocation enum.next flow of execution picked point left off.

ruby has object called fiber might demonstrate more succinctly: http://apidock.com/ruby/fiber allow 'pause execution' @ arbitrary point in program calling fiber.yield , resume left off @ later time.

for example, example above:

@names = %w[ylva brighid shifra yesamin] fiber = fiber.new   fiber.yield @names.shift # yields control caller   fiber.yield @names.shift   fiber.yield @names.shift   fiber.yield @names.shift end  # resume calls give control fiber @ point left off puts fiber.resume #=> ylva puts fiber.resume #=> brighid puts fiber.resume #=> shifra puts fiber.resume #=> yesamin