Rails 6 表关联用户表与项目表关联

Question

您好，我正在尝试创建一个包含用户正在销售的商品的应用。我有一张供销售商品的用户使用的表格和一张供商品使用的表格，但我对如何为买家设置下一张桌子有点困惑。我有一个单独的表，它在用户和项目跟踪 user_id 和 item_id 之间是多对多的。我应该创建一个类似的表来跟踪buyer_id 和item_id 吗？我希望能够跟踪从哪个用户那里购买了哪些商品，反之亦然。 User 和 Buyers 来自同一个 User 表。

谢谢！

编辑：

class UsersController < ApplicationController
  def my_page
    @user = current_user
    @seller_items = current_user.seller_orders.map { |so| so.order_items.map { |oi| { item: oi.item } } }.flatten
    @seller_items.to_a
  end
end

Answer 1

一个更完整的答案，更少的模型和命名的连接。您可能想要“合并” order 和 order_items 表，如果您正在处理单个待售物品，则删除多个表，例如汽车，但对于批量购买或可能与其他物品同时出售的任何物品，您可能需要这种布局：

生成您的模型：

rails g model User name:string
rails g model Item name:string
rails g model Order order_date:time status:string
rails g model OrderItem order:references item:references multiple:integer

修改 create_order 以添加额外的引用：

  def change
    create_table :orders do |t|
      t.time :order_date, index: true, null: false
      t.string :status
      t.references :buyer, index: true, null: false, foreign_key: {to_table: :users}
      t.references :seller, index: true, null: false, foreign_key: {to_table: :users}

      t.timestamps
    end

迁移模型：

rake db:migrate
== 20201126090851 CreateUsers: migrating ======================================
-- create_table(:users)
   -> 0.0036s
== 20201126090851 CreateUsers: migrated (0.0039s) =============================

== 20201126090858 CreateItems: migrating ======================================
-- create_table(:items)
   -> 0.0030s
== 20201126090858 CreateItems: migrated (0.0032s) =============================

== 20201126091129 CreateOrders: migrating =====================================
-- create_table(:orders)
   -> 0.0077s
== 20201126091129 CreateOrders: migrated (0.0081s) ============================

== 20201126091209 CreateOrderItems: migrating =================================
-- create_table(:order_items)
   -> 0.0065s
== 20201126091209 CreateOrderItems: migrated (0.0067s) ========================

修改模型以添加连接：

app/models/user.rb
::::::::::::::
class User < ApplicationRecord
  has_many :buyer_orders, class_name: "Order", foreign_key: :buyer, inverse_of: :buyer
  has_many :seller_orders, class_name: "Order", foreign_key: :seller, inverse_of: :seller
end
::::::::::::::
app/models/item.rb
::::::::::::::
class Item < ApplicationRecord
  has_many :order_items, inverse_of: :item
end
::::::::::::::
app/models/order.rb
::::::::::::::
class Order < ApplicationRecord
  has_many :order_items, inverse_of: :order
  belongs_to :seller, class_name: "User", inverse_of: :seller_orders
  belongs_to :buyer, class_name: "User", inverse_of: :buyer_orders
end
::::::::::::::
app/models/order_item.rb
::::::::::::::
class OrderItem < ApplicationRecord
  belongs_to :order, inverse_of: :order_items
  belongs_to :item, inverse_of: :order_items
end

插入数据：

User.create(name: "hello")
User.create(name: "again")
Item.create(name: "whatever")
Order.create(buyer: User.first, seller: User.last, order_date: Time.now())
OrderItem.create(item: Item.first, order: Order.first, multiple: 1)

测试输出：

查看订单状态：

2.7.0 :002 > Order.first
   (0.5ms)  SELECT sqlite_version(*)
  Order Load (0.2ms)  SELECT "orders".* FROM "orders" ORDER BY "orders"."id" ASC LIMIT ?  [["LIMIT", 1]]
 => #<Order id: 1, order_date: "2000-01-01 09:26:22", status: nil, buyer_id: 1, seller_id: 2, created_at: "2020-11-26 09:26:22", updated_at: "2020-11-26 09:26:22">

2.7.0 :003 > Order.first.seller
  Order Load (0.2ms)  SELECT "orders".* FROM "orders" ORDER BY "orders"."id" ASC LIMIT ?  [["LIMIT", 1]]
  User Load (0.3ms)  SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 2], ["LIMIT", 1]]
 => #<User id: 2, name: "again", created_at: "2020-11-26 09:25:26", updated_at: "2020-11-26 09:25:26">

2.7.0 :004 > Order.first.buyer
  Order Load (0.2ms)  SELECT "orders".* FROM "orders" ORDER BY "orders"."id" ASC LIMIT ?  [["LIMIT", 1]]
  User Load (0.2ms)  SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 1], ["LIMIT", 1]]
 => #<User id: 1, name: "hello", created_at: "2020-11-26 09:25:18", updated_at: "2020-11-26 09:25:18">

查看第一个用户的“买家订单”：

2.7.0 :013 > User.first.buyer_orders
  User Load (0.2ms)  SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT ?  [["LIMIT", 1]]
  Order Load (0.3ms)  SELECT "orders".* FROM "orders" WHERE "orders"."buyer_id" = ? LIMIT ?  [["buyer_id", 1], ["LIMIT", 11]]
 => #<ActiveRecord::Associations::CollectionProxy [#<Order id: 1, order_date: "2000-01-01 09:26:22", status: nil, buyer_id: 1, seller_id: 2, created_at: "2020-11-26 09:26:22", updated_at: "2020-11-26 09:26:22">]>

查看第二个用户的“卖家订单”：

2.7.0 :014 > User.last.seller_orders
  User Load (0.2ms)  SELECT "users".* FROM "users" ORDER BY "users"."id" DESC LIMIT ?  [["LIMIT", 1]]
  Order Load (0.3ms)  SELECT "orders".* FROM "orders" WHERE "orders"."seller_id" = ? LIMIT ?  [["seller_id", 2], ["LIMIT", 11]]
 => #<ActiveRecord::Associations::CollectionProxy [#<Order id: 1, order_date: "2000-01-01 09:26:22", status: nil, buyer_id: 1, seller_id: 2, created_at: "2020-11-26 09:26:22", updated_at: "2020-11-26 09:26:22">]>

为了安心，请检查第一个用户是否没有任何卖家订单：

2.7.0 :015 > User.first.seller_orders
  User Load (0.2ms)  SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT ?  [["LIMIT", 1]]
  Order Load (0.2ms)  SELECT "orders".* FROM "orders" WHERE "orders"."seller_id" = ? LIMIT ?  [["seller_id", 1], ["LIMIT", 11]]
 => #<ActiveRecord::Associations::CollectionProxy []>
2.7.0 :016 >

控制器

class UsersController < ApplicationController
  def my_page
    @user = current_user
    @seller_orders = current_user.seller_orders
    # remember that you might want to filter this in the future
    # from_date = params[:from_date].present? ? params[:from_date] : Time.at(0)
    # to_date = params[:to_date].present? ? params[:to_date] : Time.now()
    # @seller_orders = @seller_orders.where(order_date: from_date..to_date)
  end
end

查看（我用的是haml）

%h1
  = @user.username
  Seller Orders

- @seller_orders.each do |so|
  %table.seller_order{id: "seller_order_#{so.id}"}
    %tr
      %th Order Date:
      %td= so.order_date
    %tr
      %th Buyer:
      %td= so.buyer.username
    %tr.spacer
      %td{colspan: 2}  
    %tr
      %th Item
      %th Multiple
    - so.order_items.each do |oi|
      %tr
        %td= oi.item.name
        %td= oi.multiple

卖家商品

@seller_items = @seller_orders.map{|so| so.order_items.map{|oi| {multiple: oi.multiple, item: oi.item} }.flatten

或者可能（从内存中写入，未经测试）

@seller_items = OrderItem.select("sum(order_items.multiple) as multiple, order_items.item_id as item_id").joins(:orders).joins(:buyer).where("users.id = ?", User.first.id).group("item_id")

Answer 2

你确实需要一些中间的东西——这在电子商务中通常被称为“订单”：

• 链接到用户
• 项目链接

但也许还有更多属性：

• 销售日期
• 状态（购物车/订单/已付款/已交付）

确实如此 - 你会想要一个额外的模型

Answer 3

class Seller < ApplicationRecord
  belongs_to :user
  has_many selling_items
  has_many :items, through: :selling_items
end

class Buyer < ApplicationRecord
  belongs_to :user
  has_many bought_items
  has_many :items, through: :bought_items
end

class Items < ApplicationRecord
end

class BoughtItem < ApplicationRecord
  belongs_to :buyer
  belongs_to :item
end

class SellingItem < ApplicationRecord
  belongs_to :seller
  belongs_to :item
end

class User < ApplicationRecord
end