Question

I am programming a booking system.
I want my users to be able to book only one (or a defined number of) resources at a time. However, I do not want to remove “past” reservation for my database, since it will be used for invoicing purposes. On reservation creation, I need to validate that a user has not exceeded its reservation quota, which means has not more than “quota” reservations in the future.

class User < ActiveRecord::Base
    has_many :reservations

    def active_reservations
        #maybe worth to rewrite with a "find"?
        my_list = []
        reservations.each do |reservation|
        if (not reservation.past?)
            my_list.push(reservation)
        end
        return my_list
    end

class Reservation < ActiveRecord::Base
    belongs_to :user
    validate :respect_user_quota
    def past?
        return (date < Date.now)

    def respect_user_quota
        if (user.active_reservations.count > user.quota)
            errors.add(:user, "User quota exceeded!")

Is this the right way to implement this validation? What could be wrong there (I never see the error message). Should the quota validation be moved to the user class?

Answer 1

I would try and do this more simply and move the validation to user.

class User < ActiveRecord::Base
  has_many :reservations

  validate :reservation_quota
    if sum(reservations.active) > quota  # User.quota is implied here
      errors.add(:user, "User quota exceeded!")
    end

class Reservation < ActiveRecord::Base
  belongs_to :user
  def active
    active? 1 : 0  
     # If there's a boolean 'active' flag the ? method gets created automatically.    
     # This could be (reservation_date < Date.now)? ? 1 : 0 for you.
     # Using `(expression)? ? true : false` is using the Ternary operator. 
  end
end