From: Phrogz <phrogz@...>
Date: 2009-03-31T05:14:54+09:00
Subject: Re: When to use instance variables @

On Mar 30, 2:05 pm, Phrogz <phr...@mac.com> wrote:
> Class 'declarations' aren't quite what you think they are. They're
> actually code that is executed. Try this on for size:

Here's a more real example of why you might want to write arbitrary
code while creating (or modifying) a class:

class Person
  %w| age weight sex |.each do |param|
    variable_name = "@#{param}".to_sym
    define_method( param ) do
      puts "You just accessed #{param}"
      instance_variable_get( variable_name )
    end
    define_method( "#{param}=" ) do |new_value|
      puts "Now setting #{param} to #{new_value}"
      instance_variable_set( variable_name, new_value )
    end
  end
end

me = Person.new

me.age = 42
#=> "Now setting age to 42"

puts me.age
#=> "You just accessed age"
#=> 42