Sample Query Object

query_object.rb

class OrdersQuery
  def initialize(relation = Order.all)
    @relation = relation.extending(Scopes)
  end

  def find
    @relation.includes(:order_state, 
      :region, 
      :merchant_payment_method_currency => [ 
        :merchant, :payment_method_currency => [ :payment_method_branch ]
      ],
      :merchant_withdraw => :currency).recent_first
  end


  module Scopes
    include BaseQuery

    def for_a_merchant(merchant_id)
      where("merchants.id" => merchant_id).references(:merchants)
    end

    def for_a_region(region_id)
      return self if region_id.blank?
      where("regions.id = ?", region_id).references(:regions)
    end

    def for_payment_method_branches(*payment_method_branch_ids)
      return self if payment_method_branch_ids.blank_ext?
      where("payment_method_branches.id" => payment_method_branch_ids).references(:payment_method_branches)
    end

    def for_withdraw_currencies(*currency_ids)
      return self if currency_ids.blank_ext?
      where("currencies.id" => currency_ids).references(:currencies)
    end

    def for_order_states(*states)
      return self if states.blank_ext?
      where("order_states.name" => states).references(:order_states)
    end

    def recent_first
      order("orders.created_at DESC")
    end
  end
end