rspec users - Dec 2006 - should_receive and multiple return values

Hi

I just got bit by a misunderstanding about and_return.

I''ve got this controller method parse_parameters that loops over  
query string parameters and parses out vehicle registration dates.   
We have to turn these into one of three bands (Jan-Feb, Mar-Aug, Sep- 
Dec) so I wrote a method (registration_date_to_band_year_and_month)  
takes a date and returns two return values, the year and month of the  
band.

I thought this would work:

   specify "should turn the provided registration date into a CAP  
band" do
     CapFutureResidual.should_receive 
(:registration_date_to_band_year_and_month).with(Date.new(2003, 9,  
30)).and_return(2003, 9)
     CapFutureResidual.should_receive 
(:registration_date_to_band_year_and_month).with(Date.new(2005, 3,  
1)).and_return(2005, 3)
     controller.parse_parameters(
         { :capid26149 => "rd2003-09-30,mi40000,ft15", :capid30125
=>
"rd2005-03-01,mi73825,ft42" }
       )
   end

But it doesn''t because and_return is setting up multiple method  
calls, not multiple return values.

I don''t imagine multiple return values are used that often, but they  
can be handy.  Would there be any use in another method, maybe  
and_return_values or something to allow you to specify them?  Since  
they are possible in Ruby, it makes sense that you should be able to  
specify them in RSpec.

I got around it, of course, using an array return and the * expand  
operator, but I avoid that when I can

Ashley

On 12/18/06, Ashley Moran <work at ashleymoran.me.uk>
wrote:
> Hi
>
> I just got bit by a misunderstanding about and_return.
>
> I''ve got this controller method parse_parameters that loops over
> query string parameters and parses out vehicle registration dates.
> We have to turn these into one of three bands (Jan-Feb, Mar-Aug, Sep-
> Dec) so I wrote a method (registration_date_to_band_year_and_month)
> takes a date and returns two return values, the year and month of the
> band.
>
> I thought this would work:
>
>    specify "should turn the provided registration date into a CAP
> band" do
>      CapFutureResidual.should_receive
> (:registration_date_to_band_year_and_month).with(Date.new(2003, 9,
> 30)).and_return(2003, 9)
>      CapFutureResidual.should_receive
> (:registration_date_to_band_year_and_month).with(Date.new(2005, 3,
> 1)).and_return(2005, 3)
>      controller.parse_parameters(
>          { :capid26149 => "rd2003-09-30,mi40000,ft15",
:capid30125 =>
> "rd2005-03-01,mi73825,ft42" }
>        )
>    end
>
> But it doesn''t because and_return is setting up multiple method
> calls, not multiple return values.
>
> I don''t imagine multiple return values are used that often, but
they
> can be handy.  Would there be any use in another method, maybe
> and_return_values or something to allow you to specify them?  Since
> they are possible in Ruby, it makes sense that you should be able to
> specify them in RSpec.
>
> I got around it, of course, using an array return and the * expand
> operator, but I avoid that when I can
>
> Ashley
hrm...when you return multiple values, isn''t it actually returning an
array?

irb(main):001:0> def foo; return 1, 2; end
=> nil
irb(main):002:0> a = foo
=> [1, 2]
irb(main):003:0> b, c = foo
=> [1, 2]
irb(main):004:0> a
=> [1, 2]
irb(main):005:0> b
=> 1
irb(main):006:0> c
=> 2

It''s just that Ruby is smart enough that you don''t need the []
in the
return value.  Also, doing multiple assignment works even if you
explicitly return an array:
irb(main):001:0> def foo; return [1, 2]; end
=> nil
irb(main):002:0> a, b = foo
=> [1, 2]
irb(main):003:0> a
=> 1
irb(main):004:0> b
=> 2

So it really should just be and_return([2005, 3])

Pat

On 18 Dec 2006, at 12:31, Pat Maddox wrote:
> So it really should just be and_return([2005, 3])
>
> Pat

Cool.  I never realised that... if I''d changed my spec *first* like  
I''m supposed to I would have noticed it worked :)

Thanks
Ashley