From: Eric Hodel <drbrain@...7.net>
Date: 2007-01-03T04:35:50+09:00
Subject: Re: Detecting default used in method calls

On Jan 2, 2007, at 07:31, Peter Lynch wrote:

> I would like to know if a function has been called with or without an
> optional argument.
>
> If I have -
>
>  def the_Function (a, b = '')
>  end
>
> and I invoke it like this -
>
>  the_Function('a')
>  the_Function('a', '')
>
> is there any way for me to tell within the_Function which form of
> invocation was used?

No need to do those complicated things that everybody else is  
trying.  Instead use an object that nobody else will pass you as a  
sentinel:

class X

   SENTINEL = Object.new

   def the_function(a, b = SENTINEL)
     if b == SENTINEL then
       ...
     end
   end

end

-- 
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net

I LIT YOUR GEM ON FIRE!



-- 
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net

I LIT YOUR GEM ON FIRE!



-- 
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net

I LIT YOUR GEM ON FIRE!