gistfile1.rb

module MyAccessors
  def my_attr_accessor(property_name)
       send(:define_method, property_name) do
         instance_variable_get("@#{property_name}")
       end

       send(:define_method, "#{property_name}=") do |value|
         instance_variable_set("@#{property_name}", value)
       end
  end
end


class Foo
  extend MyAccessors
  my_attr_accessor :foo
end

obj = Foo.new
obj.foo # => nil, no exception
obj.foo = 12
obj.foo # => 12

Another solution would be actually using ruby eval instead of define_method, which is probably more efficient and maybe even more clear code, but I have an instinctive irrational desire to always avoid eval. But the eval approach is I think what I've seen in for instance Rails source that does things similar to this.