From: Hugh Sasse Staff Elec Eng <hgs@...>
Date: 2002-02-14T00:09:36+09:00
Subject: Re: qualms about respond_to? idiom

On Wed, 13 Feb 2002, David Alan Black wrote:

> Hi --
>
> I'm cool with Ruby's emphasis on object interface rather than type.
> The only thing is...  I just can't get myself to be happy about this
> idiom:
>
>    if obj.respond_to? "method" then obj.method end
>
> I'm not sure how to express what I don't like about it -- but I guess
> the sheer repetitiveness of it, mainly.  It always looks and feels
> like a kind of workaround to me, or like something is being done
> manually that should somehow just happen.

Also the failure of the if clause raises the question about what to put
in the else clause.

TRCR - tentative ruby change request:

define respond_to_these? accepting an array as its first parameter, then
one could test all the methods at once, to check the interface before
you set out.

define Object::these_respond_to? accepting a hash as the first
parameter, then one could do

    Object::respond_to?({ aRegexp => "match", aString => ">>",
                          anInstance => "each"})

and test a bunch of parameters at the outset.

>
> David
        Hugh