From: dblack@...
Date: 2003-01-17T10:25:07+09:00
Subject: Re: quick: it responds, it evaluates, and is not empty

Hi --

On Fri, 17 Jan 2003, ahoward wrote:

> On Fri, 17 Jan 2003, Tom Sawyer wrote:
>
> > quick quest: anyone know of a nice slick short and sweet way to do this:
> >
> > 	if self.respond_to?(:ameth)
> > 		if ameth
> > 			if not ameth.to_s.empty?
> > 				...
> > 			end
> > 		end
> > 	end
>
> i'm assuming :ameth and ameth are meant to be a Symbol and String
> respectively, otherwise the 2nd and 3rd calls would be meaningless since the
> call to respond_to? would have failed so
>
> respond_to? :ameth and ameth and not ameth.to_s.empty? ...
>
> short ciruits the same way.  not that short... but potentially one line.
>
> it's hard to envision why simply
>
>   ... if respond_to ameth
>
> would not suffice though?  why have :ameth and ameth?

Because if you just have respond_to?(ameth), then ameth will
be evaluated (method call or local variable), which probably
isn't what's wanted.

  irb(main):005:0> "".respond_to?(:blah)
  false
  irb(main):006:0> "".respond_to?(blah)
  NameError: undefined local variable or method `blah' for
      #<Object:0x401ccce0> from (irb):6


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav