Query Object with Active Record

example.rb

class Filters
  class Base
    attr_reader :scope

    def initialize(scope)
      @scope = scope
    end
  end

  class ByPrice < Base
    def call(price:, **_options)
      return scope if price.nil?

      scope.where(price: price)
    end
  end

  class ByName
    def call(name:, **_options)
      return scope if name.nil?

      scope.where('name ILIKE ?', "%#{name}%")
    end
  end

  class Paginate
    PER_PAGE = 10

    def call(page:, per_page: PER_PAGE, **_options)
      # default kaminari methods
      scope.page(page).per(per_page) 
    end
  end

  class OrderBy
    def call(order_by:, order_direction:, **_options)
      scope.order(order_by => order_direction)
    end
  end
end


class ProductFilter
  # params 
  # => { price: 100_000, name: 'Apple', page: 2, order_by: created_at, order_direction: :asc }
  def call(params)
    [
      Filters::ByPrice,
      Filters::ByName,
      Filters::OrderBy,
      Filters::Paginate
    ].inject(Product.all) { |scope, klass| scope = klass.new(scope).call(params) }
  end
end