my_attr_accessor.rb

class A
  def self.my_attr_accessor(attr)
    define_method "#{attr}" do
      instance_variable_get("@#{attr}")
    end

    define_method "#{attr}=" do |param|
      instance_variable_set("@#{attr}", param)
    end
  end

  my_attr_accessor :name

  def initialize(name)
    @name = name
  end
end

a = A.new("kk")
puts a.name
a.name = "yy"
puts a.name