From: James Mead <jamesmead44@...>
Date: 2009-11-26T21:36:17+09:00
Subject: Re: Mocha multiple_yields with arrays

2009/11/26 Raymond O'Connor <nappin713@yahoo.com>:
> I believe there's a bug in mocha that causes an unnecessary and annoying
> warning message.  If you call multiple_yields with arrays as the arg you
> want yielded it will complain.
>
> object.multiple_yields([1,2], [3,4], [5,6])
>
> => prints a warning to the effect: "multiple values for a block
> parameter 2 for 1"

That code snippet looks wrong. The multiple_yields method is a method
on an expectation, so you must call it on the result of e.g.
object.stubs or object.expects. I suspect this was a typo and assume
you meant something more like this :-

  object.stubs(:wibble).multiple_yields([1,2], [3,4], [5,6])

In this case, Mocha will invoke the block supplied to the wibble
method 3 times and passing in 2 parameters on each invocation.

If you supply a block which defines only one parameter you will see
the warning you described :-

  parameters = []
  object.wibble { |parameter| parameters << parameter }
  # => warning: multiple values for a block parameter (2 for 1)
  p parameters # => [[1,2], [3,4], [5,6]]

If you supply a block which defines two parameters you will not see
the warning :-

  parameters = []
  object.wibble { |parameter_1, parameter_2| parameters <<
[parameter_1, parameter_2] }
  p parameters # => [[1,2], [3,4], [5,6]]

So the warning you are seeing is not a problem with Mocha, but due to
normal Ruby behaviour which you can see in irb :-

irb> def wibble
irb>   yield(1,2)
irb> end
=> nil
irb> wibble { |x| p x }
(irb):4: warning: multiple values for a block parameter (2 for 1)
	from (irb):2
[1, 2]
=> nil
irb> wibble { |x,y| p [x,y] }
[1, 2]
=> nil
irb> wibble { |(x,y)| p [x,y] }
[1, 2]
=> nil

I hope this helps. If you have any further questions about this,
please post to the Mocha mailing list [1] which would be a more
appropriate forum.

Cheers, James.

[1] http://groups.google.com/group/mocha-developer