filterable.rb

module Filterable
  extend ActiveSupport::Concern

  module ClassMethods
    # filter=[created|by_phone=922480|by_id=100..1000]
    def filter(filtering_params)
      results = self.where(nil)
      if filtering_params
        filters = filtering_params.gsub(/[\[\]\{\}\'\"\(\)]/, '').split(/[\|]/)

        filters.each do |value|
          if value.present?
            if value.include?('=')
              value = value.split(/[\=]/)
              if value.respond_to?(:[]) && value.count == 2
                if value[1].include?('..')
                  between = value[1].split(/\.\./)
                  if between.respond_to?(:[]) && between.count == 2
                    results = results.public_send(value[0].strip, between[0].strip, between[1].strip)
                  end
                else
                  results = results.public_send(value[0].strip, value[1].strip)
                end
              end
            else
              results = results.public_send(value.strip) if value.present?
            end
          end
        end
      end
      results.distinct
    end
  end
end

...


# Возвращает список автомобилей
# @note GET /api/v1/cars
# @example GET /api/v1/cars
def index
  @cars = Car.filter(params[:filter])
end