srp_example.rb

class Moviegoer
  attr_accessor :name, :street, :phone_number, :zipcode
  validates :phone_number, # ...
  validates :zipcode, # ...
  def format_phone_number ; ... ; end
  def verify_zipcode ; ... ; end
  def format_address(street, phone_number, zipcode) # data clump
    # do formatting, calling format_phone_number and verify_zipcode
  end
end
# After applying Extract Class:
class Moviegoer
  attr_accessor :name
  has_one :address
end
class Address
  belongs_to :moviegoer
  attr_accessor :phone_number, :zipcode
  validates :phone_number, # ...
  validates :zipcode, # ...
  def format_address ; ... ; end # no arguments - operates on 'self'
  private  # no need to expose these now:
  def format_phone_number ; ... ; end
  def verify_zipcode ; ... ; end
end