gistfile1.txt

class TransactionAccount < ActiveRecord::Base
  composed_of :balance, :class_name => "Money", :mapping => [%w(cents account_balance_cents), %w(currency currency) ]

  belongs_to :user
  has_many :sent_transactions,     :class_name => "TransactionItem",
                                  :foreign_key => "transaction_sender_account_id"
  
  has_many :received_transactions, :class_name => "TransactionItem",
                                  :foreign_key => "transaction_receiver_account_id"
end

class TransactionItem < ActiveRecord::Base
  composed_of :amount, :class_name => "Money", :mapping => [%w(cents cents), %w(currency currency) ]

  belongs_to  :sender,
              :class_name => "TransactionAccount",
              :foreign_key => "transaction_sender_account_id"

  belongs_to  :receiver,
              :class_name => "TransactionAccount",
              :foreign_key => "transaction_receiver_account_id"

  belongs_to  :transaction_object,
              :polymorphic => true

  validates_presence_of :sender
  validates_presence_of :receiver
  validates_presence_of :description


  def update

  end

  def finalize
    
  end

  def receiver_amount
    amount
  end

  def sender_amount
    amount * -1
  end

  private
    validate :cents_not_zero

    def cents_not_zero
      errors.add("cents", "cannot be zero or less") unless cents > 0
    end 
end