From: Ryan Pavlik <rpav@...>
Date: 2003-11-23T17:02:13+09:00
Subject: Re: Method wrapper question (was "stereotyping (was ...))

On Sat, 22 Nov 2003 23:33:57 +0900
"Christoph" <chr_mail@gmx.net> wrote:

> ts wrote:
> ...
> >  Yes, and this is why I prefer this scheme to
> > 
> >    class A
> >       def a:pre
> >       end
> > 
> >       def a:pre
> >       end
> > 
> >       def a
> >       end
> >    end            
> 
> Agreed 100% - I see no reason for allowing several hooks in the same class.
> 
> /Christoph
> 

Hmm, actually, there are a lot of good reasons for allowing multiple
hooks in the same class.  This is, AFAIK, the point of having hooks at
all... so many people can hook into them.

For instance, you may add a method:pre hook to check some parameter
values, make sure they're in range.  You may include a package which
adds a :pre hook to add permissions.  Etc.

If you can only have one hook, what's the difference between doing
this:
    
    class Foo
       def bar:pre
         # pre stuff
       end
    
       def bar
         # body stuff
       end
    end
    

and doing this:

    class Foo
       def bar
         # pre stuff
         # body stuff
       end
    end

or even this:

    class Foo
       def bar_pre
         # pre stuff
       end

       def bar
         bar_pre
         # body stuff
       end
    end

To answer the question of order, it can either be configurable (I
think CLOS allows this) or simply "stack order" (latest defined :pre
goes first, latest defined :post goes last, etc.).

-- 
Ryan Pavlik <rpav@mephle.com>

"I wish I had arachna-powers. I would dispense death
 from the skies." - 8BT