From: Sean O'Dell <sean@...>
Date: 2004-05-28T07:15:59+09:00
Subject: Re: true.respond_to?("clone")

On Thursday 27 May 2004 15:05, David A. Black wrote:
> Hi --
>
> On Fri, 28 May 2004, Sean O'Dell wrote:
> > On Thursday 27 May 2004 14:24, Hal Fulton wrote:
> > > Sean O'Dell wrote:
> > > > TrueClass responds to "clone" but when you call it, the method just
> > > > throws an error that says "can't clone TrueClass."  How can I tell
> > > > when an objects support a given method if they implement them but
> > > > then raise exceptions?  Is there some other methodology I should use?
> > >
> > > Interesting question. I suppose you could always catch the exception
> > > and then set your own flag that says you can't clone.
> >
> > That sort of makes respond_to? less functional than advertised.
>
> It's just being very literal.
>
> > > This raises the question in my mind of whether the clone method should
> > > simply be removed from such classes.
> >
> > My feeling is, it should be removed.  I would think that the rule of
> > thumb is "if it respond_to?'s, it is implemented."
>
> What about NotImplementedError? :-)

Why have respond_to? at all then?  Why not just catch NotImplementedError 
everywhere you need to check an object before trying to call a method?

	Sean O'Dell