From: Massimiliano Mirra <list@...>
Date: 2002-10-07T17:15:05+09:00
Subject: Re: Another take on ensuring right args to methods

On Sun, Oct 06, 2002 at 10:43:46PM +0900, dblack@candle.superlink.net wrote:
> Personally I like #can?  but it doesn't help with the awkward two-headed
> "obj.meth if obj.can?(:meth)" idiom.

I know, but I'm still convinced that you'd only want to do that when
calling meth on obj was totally optional to the logic, which happens
seldom (at least in my experience).

> >  class Foo def meth(bar) bar.passes?(TestBar) or raise ArgumentError
> > end end Foo.new.meth(1) $ ruby --inline-tests foo.rb
> What does #passes? actually do?

Actually nothing since it's not implemented :-), but in my mind, it
would submit the object (or rather its class) to a small ad-hoc test
suite, which would not only test whether it responded to (for example)
#read, #write and #seek, but also check whether what gets written with
#write can be later read with #read.

It would impose quite an overhead at runtime, but could be executed
only when a global switch was turned on (--inline-tests), and would
guarantee that an object really provides some functionality, not just
`looks like to' as with respond_to? or Java interfaces.


Massimiliano