Core associations between contract, client, code and codeline

client.rb

class Client < ActiveRecord::Base
  attr_accessible :etc, :firstname, :lastname, :mi 

  has_many :contracts

  validates :firstname, :lastname, :mi, presence: true

  def full_name
    "#{firstname} #{mi} #{lastname}"
  end 
end

code.rb

class Code < ActiveRecord::Base
  attr_accessible :codename, :description, :status

  has_many :codelines, dependent: :destroy
  has_many :contracts, through: :codelines

  validates :codename, :description, :status, presence: true
end

codeline.rb

class Codeline < ActiveRecord::Base
  belongs_to :contract
  belongs_to :code

  accepts_nested_attributes_for :code

  attr_accessible :code_attributes, :units_alloc

  validates :units_alloc, presence: true, numericality: true
end

contract.rb

class Contract < ActiveRecord::Base
  belongs_to :client

  has_many :codelines, dependent: :destroy
  has_many :codes, through: :codelines

  accepts_nested_attributes_for :codelines
  accepts_nested_attributes_for :client

  validates :authnum, :end_date, :start_date, presence: true
end