From: Rick DeNatale <rick.denatale@...>
Date: 2009-08-19T22:09:45+09:00
Subject: Re: #has_arguments?

On Tue, Aug 18, 2009 at 11:37 PM, Intransition<transfire@gmail.com> wrote:
> Messing with optional argument check for the umpteenth time, eg.
>
>  def meth(a=Exception)
>    if a != Exception
>       ...
>    else
>      ...
>    end
>  end
>
> Other's might do:
>
>  def meth(*a)
>    if !a.empty?
>      a = a.first
>       ...
>    else
>      ...
>    end
>  end
>
> Neither of which are very satisfying. So it occurs to me tonight that
> we already have #has_block? to see if a block was passed. So how about
> a #has_arguments? to query if _any_ arguments have been passed. So
> then...
>
>  def meth(a=default)
>    if has_arguments?
>       ...
>    else
>      ...
>    end
>  end
>
> Ah... now that would be nice.

I've never felt the need for this.

Normally I just make the default value for an optional parameter nil,
and check for nil.

If nil is a valid value, then I'd do something like

class A

    MissingArgument = Object.new

   def meth(a=MissingArgument)
       if a == MissingArgument
       else
       end
   end
end




-- 
Rick DeNatale

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