find_one

# File activerecord/lib/active_record/relation/finder_methods.rb, line 445
      def find_one(id)
        if ActiveRecord::Base === id
          raise ArgumentError,             You are passing an instance of ActiveRecord::Base to `find`.            Please pass the id of the object by calling `.id`..squish
        end

        relation = where(primary_key => id)
        record = relation.take

        raise_record_not_found_exception!(id, 0, 1) unless record

        record
      end