class Library::Holding < ApplicationRecord
  belongs_to :school
  belongs_to :bib
  belongs_to :location
  belongs_to :item_condition

  validates :barcode, uniqueness: { scope: :school_id }, numericality: true, allow_nil: true

  def self.next_barcode
    last_code = order(barcode: :desc).limit(1).pluck(:barcode).first
    last_code.nil? ? 1 : last_code.to_i + 1
  end
end