find_by_scan

# File activerecord/lib/active_record/associations/collection_association.rb, line 521
        def find_by_scan(*args)
          expects_array = args.first.kind_of?(Array)
          ids           = args.flatten.compact.map(&:to_s).uniq

          if ids.size == 1
            id = ids.first
            record = load_target.detect { |r| id == r.id.to_s }
            expects_array ? [ record ] : record
          else
            load_target.select { |r| ids.include?(r.id.to_s) }
          end
        end