From: Ara.T.Howard@...
Date: 2004-11-06T03:13:41+09:00
Subject: Re: value provided for argument with default value - how to check inside method?

On Sat, 6 Nov 2004, Charles Mills wrote:

> On Nov 4, 2004, at 8:03 PM, itsme213 wrote:
>
>> Is there an equivalent of block_given? to check if the caller provided
>> a
>> value to an argument that had a default value?
>>
>> Or do I have to use some sentinel value?
>
> I remember Nobu had a solution for this... I can't seem to find it
> though.  I think it was something like this:
>
> > def foo(x=(nil; a=true))
> > puts a
> > end
> => nil
> > foo()
> true
> => nil
> > foo('value')
> nil
> => nil
>
> You can replace nil with the default value you want.  a will be set to
> true if a value is passed in, nil otherwise.
>
> -Charlie


you may also use something like

   def foo arg, opts = {}
     if opts.has_key? 'x'
       ...
     end
     opts.update defaults
     ...
   end

-a
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