ruby inheritance questions

bastard_northerner.rb

## irb -- best way to get this behavior?
 
# >> load 'person.rb' 
# => true
# >> jon = Bastard_Northerner.new('jon', 'stark')
# => #<Bastard_Northerner:0x007f07086781b0 @first_name="jon", @last_name="snow">
 
## person.rb -- is this the right way?
 
class Person
  attr_accessor :first_name, :last_name
 
  def initialize (first_name, last_name)
    @first_name = first_name
    self.last_name = last_name
  end
end
 
class Bastard_Northerner < Person
  # bastard_northerners default to last_name 'snow'
  def last_name= (input_str = 'snow')
    @last_name = 'snow'
  end
end