动作仅更新最后一个对象

从最后两天开始，我尝试期待应用程序中发生了什么。这是我的问题：

我的模特：

class User
has_many :orders
---
class Order
belongs_to :user
has_and_belongs_to_many :contributors, class_name: 'User'

情况：用户可以创建订单，此订单的下一个可以添加具有以下内容的贡献者（其他用户）
<%= collection_check_boxes(:order, :contributor_ids, @prac, :id, :to_s) %>

之后，在OrdersController中的自定义操作中，我将得到以下内容：

@order.contributors.each do |u|
u.orders << @order
end

在这里，我想将此订单添加到贡献者（用户）订单列表中。不幸的是，这项工作仅适用于最后的贡献者（用户）。下面从我的控制台日志：

    Started PATCH "/orders/282/zatwierdz" for 127.0.0.1 at 2014-07-01 08:48:59 +0200

Processing by OrdersController#zatwierdz as HTML
  Parameters: {"authenticity_token"=>"hxWUnazKLoS9t8bVmOAMeIxdo/KYuO33bUeuQZYgeV
k=", "id"=>"282"}
  User Load (0.0ms)  SELECT  "users".* FROM "users"  WHERE "users"."id" = 32  OR
DER BY "users"."id" ASC LIMIT 1
  Role Load (0.0ms)  SELECT  "roles".* FROM "roles"  WHERE "roles"."id" = ? LIMI
T 1  [["id", 4]]
  Order Load (0.0ms)  SELECT  "orders".* FROM "orders"  WHERE "orders"."id" = ?
 ORDER BY created_at DESC LIMIT 1  [["id", 282]]
  OrderItem Exists (0.0ms)  SELECT  1 AS one FROM "order_items"  WHERE "order_it
ems"."order_id" = ? LIMIT 1  [["order_id", 282]]
   (0.0ms)  begin transaction
  SQL (0.0ms)  UPDATE "orders" SET "status" = ?, "updated_at" = ? WHERE "orders"
."id" = 282  [["status", 1], ["updated_at", "2014-07-01 06:48:59.486472"]]
   (62.5ms)  commit transaction
  User Load (0.0ms)  SELECT "users".* FROM "users" INNER JOIN "orders_users" ON
"users"."id" = "orders_users"."user_id" WHERE "orders_users"."order_id" = ?  [["
order_id", 282]]
   (0.0ms)  begin transaction
   (0.0ms)  commit transaction
   (0.0ms)  begin transaction
  SQL (0.0ms)  UPDATE "orders" SET "updated_at" = ?, "user_id" = ? WHERE "orders
"."id" = 282  [["updated_at", "2014-07-01 06:48:59.564595"], ["user_id", 33]]
   (78.1ms)  commit transaction
   (0.0ms)  begin transaction
  SQL (0.0ms)  UPDATE "orders" SET "updated_at" = ?, "user_id" = ? WHERE "orders
"."id" = 282  [["updated_at", "2014-07-01 06:48:59.642719"], ["user_id", 35]]
   (78.1ms)  commit transaction
   (0.0ms)  begin transaction
  SQL (0.0ms)  UPDATE "orders" SET "updated_at" = ?, "user_id" = ? WHERE "orders
"."id" = 282  [["updated_at", "2014-07-01 06:48:59.720842"], ["user_id", 36]]
   (109.4ms)  commit transaction
   (0.0ms)  begin transaction
  SQL (0.0ms)  UPDATE "orders" SET "updated_at" = ?, "user_id" = ? WHERE "orders
"."id" = 282  [["updated_at", "2014-07-01 06:48:59.830215"], ["user_id", 37]]
   (78.1ms)  commit transaction
Redirected to http://localhost:3000/orders/282
Completed 302 Found in 437ms (ActiveRecord: 406.2ms)

我尝试将此操作与回调以及模型方法一起使用，但是什么也没发生。也许更好的办法是使用其他关联？Annny表示欢迎。谢谢。