discount.rb

#overlapping dates check validations

  validate :start_date_must_be_before_end_date
  validate :overlapping_dates

  private

  def start_date_must_be_before_end_date
    if start_date > end_date
      errors.add_to_base "Start date must be before end date"
    end
  end

  def overlapping_dates
    overlap_conditions = [ '  ( ( start_date >= :ad AND end_date <= :dd )
          OR ( start_date <= :ad AND end_date >= :dd )
          OR ( start_date <= :ad AND end_date > :ad )
          OR ( start_date < :dd AND end_date >= :dd ) )
        ' + ( id != nil ? ' AND ( id != :self ) ' : '' ) + '
        ', {  :ad => start_date, :dd => end_date, :self => id } ]
    existing_discounts  = Discount.find(:all, :conditions=>overlap_conditions)
    errors.add_to_base("Dates overlap with existing discounts") if existing_discounts.size > 0
  end