Metaprogramming in Ruby

Reimplement attr_accessor

#!/usr/bin/env ruby

module Accessor

   def my_attr_accessor(name)

      STDERR.print "#{name}\n"

      ivar_name = "@#{name}"

      define_method(name) do
        STDERR.print "Get #{name}\n"
        instance_variable_get(ivar_name)
      end

      define_method("#{name}=") do |val|
        STDERR.print "Set #{name} = #{val}\n"
        instance_variable_set(ivar_name, val)
      end

   end
end

class Example
   extend Accessor
   my_attr_accessor :var
   my_attr_accessor :tst
end

ex = Example.new

ex.var = 99

puts ex.var


ex.tst = 2

puts ex.tst

Output

vega:~ plh$ !./
./meta.rb 
var
tst
Set var = 99
Get var
99
Set tst = 2
Get tst
2