From: Ara.T.Howard@...
Date: 2005-04-30T07:24:28+09:00
Subject: Re: Could you tell me if this is good meta programming style?

On Fri, 29 Apr 2005, Vincent Foley wrote:

> Hi everyone,
>
> I finished playing yet another game of Chrono Trigger the other day,
> and I thought I would look at how I could implement a simple Character
> system in Ruby.  I have the following initialize method, but I would
> like to be sure it's not extremely bad style:
>
> class Character
>  attr_accessor :strength, :magic, :defense, :magic_defense
>
>  def initialize(args = {})
>    args.each do |k, v|
>      instance_variable_set("@#{k}", v) if respond_to?(k)
>    end
>
>    methods.grep(/\w=$/).each { |setter|
>      getter = setter[0..-2]
>      if send(getter).nil?
>        send(setter, 0)
>      end
>    }
>  end
> end
>
> So, if I added a :critical_rate accessor, I wouldn't need to modify
> anything else in the initialize method.  Also, I don't want nil in any
> attribute.  Is this good style?  Are there other (maybe better) ways to
> accomplish this?  Thank you.

using my attributes module this would be

   harp:~ > cat a.rb
   require 'yaml'
   require 'attributes'

   class Character
     attributes %w( strength magic defense magic_defense )

     def initialize  args = {}
       args.each{|k,v| send k, v if respond_to? k}
       reader_attributes.each{|at| send at, 0 unless send at}
     end
   end

   c = Character::new 'strength' => 4, 'magic' => 2
   y c

   harp:~ > ruby a.rb
   --- !ruby/object:Character
   defense: 0
   magic: 2
   magic_defense: 0
   strength: 4

this works because an attribute's reader delegates to the writer if called with
an argument (send at, 0).

not sure if this is 'better' but it's shorter ;-)

cheers.

-a
-- 
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