account.rb

class Account < ActiveRecord::Base
  belongs_to :owner,  :class_name => 'User', :foreign_key => 'user_id'
  has_many :users
  has_many :transactions
  has_many :websites
  has_many :campaigns
  
  def display_name
    company || full_name || ''
  end
  
  def full_name
    "#{first_name.capitalize}, #{last_name.capitalize}" if first_name && last_name
  end
  
  def withdraw amount
      Transaction.create(
        :account => self,
        :type => 'debit',
        :amount => amount,
        :success => true
      )
      self.credit -= amount
      self.save
  end
  
  def deposit amount
    Transaction.create(
      :account => self,
      :type => 'debit',
      :amount => amount,
      :success => true
    )
    self.credit += amount
    self.save
  end
end

controller.rb

  # GET /accounts/new
  # GET /accounts/new.xml
  def signup
    self.class.layout 'sessions'
    
    @account = Account.new
    @user = User.new
    respond_to do |format|
      format.html # new.html.erb
      format.xml  { render :xml => @account }
    end
  end