From: Robert Klemme <bob.news@...>
Date: 2005-01-13T20:51:17+09:00
Subject: Re: Kernel#eval and class definition


"Pit Capitain" <pit@capitain.de> schrieb im Newsbeitrag
news:41E64CD5.6010703@capitain.de...
> Robert Klemme schrieb:
> > "Joel VanderWerf" <vjoel@PATH.Berkeley.EDU> schrieb im Newsbeitrag
> > news:41E55294.2040102@path.berkeley.edu...
> >>Better, in the sense that it takes a block (see below). But evaling a
> >>string to define the body of the class allows you to interpolate.
> >>
> >>def f(arg)
> >>   Class.new do
> >>     define_method :g do arg end
> >>   end
> >>end
> >>
> >>puts f("hello").new.g  # ==> hello
> >
> >
> > You can even use the def syntax:
> >
> > irb(main):001:0> cl = Class.new do
> > irb(main):002:1* def foo() "bar" end
> > irb(main):003:1> end
> > => #<Class:0x10186208>
> > irb(main):004:0> cl.new.foo
> > => "bar"
> >
> > That's better because then you can define methods that deal with
blocks,
> > which you can't with define_method:
> >
> > irb(main):005:0> cl = Class.new do
> > irb(main):006:1* def foo() yield "bar" end
> > irb(main):007:1> end
> > => #<Class:0x10172468>
> > irb(main):008:0> cl.new.foo {|x| p x}
> > "bar"
> > => nil
>
> The def syntax lets you define methods with blocks, but it doesn't let
you use
> objects from the defining scope, as Joel has been doing in his example.
Note
> that he passes an object into the defining method and accesses this very
object
> from the new class. You can't do that with the def syntax AFAIK.

Yeah, true.  So then both have their pros and cons.  Thanks for the
reminder!

Kind regards

    robert