ruby - Add a Business logic class to another model in Rails -

i've been given assignment i'm totally stuck on.

i've got 2 classes:

#/app/models/numbers.rb class numbers < activerecord::base   # model has(:id, :list_length, :number_list)    # array of integers   serialize :number_list    #generate number list   def create_list     array.new(self.list_length).map!{rand(100)}   end    def initialize(*params)     super     if !params.compact.empty?       self.number_list = create_list     end   end  end 

and:

#/lib/update.rb class update   #takes array of integers   def initialize(num_list)     @num_list = num_list   end    def add_rand     to_add = rand(10)     @num_list.each{|n| n += to_add}   end    def get_list     @num_list   end end 

so, update has remain library class need able instantiate numbers object , call update class methods on update num_list attribute.

so after creating numbers object, let's call @num_obj, need call @num_obj.add_rand , save updated @num_obj.num_list array database.

i'm allowed add helpers , modules like. after hours , hours of bashing away @ i'm totally lost , i'm sure it's simple haven't learned yet (and overlooked in hours of searching). point me in right direction?

edit: after more reading , couple of suggestions, changed num_list in numbers class numbers_list make things clearer

i added module:

#/lib/num.rb module num   def add_rand     temp = update.new(self.number_list)     self.number_list = temp.add_rand   end    def get_list     temp = update.new(self.number_list)     temp.get_list   end end 

and add 'include num' numbers class.

now can take numbers object , call update methods on it. works, i'm not sure if there's more elegant way it....

edit: turns out isn't right, either. gotta have update persist somehow get_list method returns update's num_list

it sounds trying separate active record model how update (business logic). might want take @ using decorator pattern:

class numberupdatedecorator < simpledelegator   def add_rand     number_list.each { |number| number += rand(10) }     save!   end end 

the usage in code:

numbers.find_each |number|   numberupdatedecorator.new(number).add_rand end 

also, might simplify things change numbers class number. add numbercollection model has many numbers. way not dealing trying serialize / deserialize list.