gistfile1.txt

class Account < ActiveRecord::Base
  has_many :account_transactions, :as => :debit_account
  has_many :account_transactions, :as => :credit_account

  def credits
    return AccountTransaction.find(:all, :conditions => {:credit_account_id => self.id})
  end
  
  def debits
    return AccountTransaction.find(:all, :conditions => {:debit_account_id => self.id})
  end

  def balance
    if [Account::ASSETS, Account::EXPENSE].include?(self.type_constant)
      # Balances on the credit side of these accounts are total positive
      return self.credit - self.debit 
    else
      # Balances on the debit side of these accounts are total positive
      return self.debit - self.credit
    end
  end

end


class AccountTransaction < ActiveRecord::Base
  belongs_to :credit_account, :polymorphic => true
  belongs_to :debit_account, :polymorphic => true
end

# How come that this is messed up?

# AccountTransaction.new(Account.find_by_name("Bank"), Account.find_by_name("Goods delivered"), 500)
# AccountTransaction.new(Account.find_by_name("Bank"), Account.find_by_name("Foobar"), 200)
# AccountTransaction.new(Account.find_by_name("Foobar"), Account.find_by_name("Bank"), 200)
#
# acc = Account.find_by_name("Bank")
# acc.account_transactions.count # 2 instead of 3!
# acc.credits.count # 2 - correct
# acc.debits.count # 1 - correct
# acc.balance # 500 - correct