gistfile1.rb

class Charge < ActiveRecord::Base
  CHARGE_TYPES = ["upload", "storage", "deposit"]

  belongs_to :member
  default_scope :order => "charges.updated_at DESC"
  
  validates_presence_of :name, :unit_price, :quantity
  validates_inclusion_of :charge_type, :in => CHARGE_TYPES
  validates_inclusion_of :chargeable_type, :in => %w(Payment VideoUpload)
  
  before_save :adjust_unit_price
  after_create :adjust_member_balance!
  
  def total
    self.unit_price * self.quantity
  end
  
  private 
    def adjust_unit_price
      return if unit_price.nil?
      val = BigDecimal.new(unit_price.to_s)
      val = self.charge_type == "deposit" ? val.abs : val.abs * -1
      self.unit_price = val
    end

    def adjust_member_balance!
      self.member.balance = member.balance + total
      self.member.save!
    end
end