Instance methods for ActiveRecord to fetch the "neighbor" records

neighbor_records.rb

module NeighborRecords
  def previous_one(col_name = :id)
    condition = self.class.arel_table[col_name].lt(public_send(col_name))
    self.class.where(condition).order(col_name => :desc).first
  end

  def next_one(col_name = :id)
    condition = self.class.arel_table[col_name].gt(public_send(col_name))
    self.class.where(condition).order(col_name => :asc).first
  end
end