From: Holden Glova <dsafari@...>
Date: 2002-06-04T15:54:40+09:00
Subject: Re: dynamic attr_accessor??

On Tue, 04 Jun 2002 02:58, you wrote:
> thanks for your tip.
>
> does one of the two possible solutions have any significant
> advantages over the other or is this just a matter of style??
>
> is one more like "the ruby way" ??
>
> markus
>
> Yukihiro Matsumoto wrote:
> > Hi,
> >
> > In message "dynamic attr_accessor??"
> >
> >     on 02/06/03, Markus Jais <mjais@web.de> writes:
> > |I like to create methods for my class dynamically based on
> > |strings I pass to initialize
> >
> >  a) attr_accessor is a method of a class
> >  b) attr_accessor takes names of accessors
> >  c) attr_accessor just defines two methods
> >
> > So the answer should be
> >
> > easier one:
> >
> > class Cl
> >    def initialize(name)
> >      @name = name
> >      self.instance_eval "
> >        def #{name}; @#{name}; end
> >        def #{name}=(val); @#{name}=val; end
> >      "
> >    end
> > end
> >
> > trickier one:
> >
> > class Cl
> >    def initialize(name)
> >      @name = name
> >      class <<self
> >        self
> >      end.module_eval{attr_accessor name}
> >    end
> > end
> >
> > matz.

I personally prefer the non-eval way that Guy Decoux recommend of using 
type.__send__. Try and not use eval whenever you can IMO - plus I think the 
clarity is enhanced in many non-eval solutions.

irb(main):019:0> class A
irb(main):020:1> def initialize(name)
irb(main):021:2> @name = name
irb(main):022:2> type.__send__(:attr_accessor, "name")
irb(main):023:2> end
irb(main):024:1> end
nil
irb(main):025:0> a = A.new('billy')
#<A:0x404f4318 @name="billy">
irb(main):026:0> a.name
"billy"
irb(main):027:0> a.name = 'Freddy'
"Freddy"
irb(main):028:0> a.inspect
"#<A:0x404f4318 @name=\"Freddy\">"


-- 
Signed,
Holden Glova