Rails 5：带有迭代的数据库设计 [英] Rails 5: Database design with iterations

问题描述

我目前有一个包含用户，餐食和订单表的站点。

I currently have a site with Users, Meals, and Orders tables.

• 用户表保存用户信息


• 膳食表中包含膳食名称，描述，img（url）

我当前正在使用迭代：

<% @meals.each do |meal| %>
 <%= image_tag(meal.img,  alt: meal.name) %>
 <span class="mealname"><%= meal.name %></span>
 <p><%= meal.description %><p>

   <div class="qty">
       INPUT FOR ORDER QTYS HERE
   </div>

<% end %>

• 订单表包含用户想要的每顿饭的数量



订单迁移以供参考：

  t.belongs_to :user
  t.integer :total_meals, null: false, default:"0"
  t.integer :meal1, null: false, default: "0"
  t.integer :meal2, null: false, default: "0"
  etc..

在我之前不是使用迭代，而是使进餐1，进餐2等与HTML布局中的餐相匹配。

Before I was not using an iteration and had the respective meal1, meal2, etc matching up to the Meals in the HTML layout.

这显然可以做得更好，但是考虑到我需要膳食信息能够动态更新（我想使用上面的迭代），我应该如何处理呢？

This obviously can be done better, however considering I need the Meals information to be able to be updated dynamically (I want to use the iteration above), How should I go about dealing with this?

但是...如果我使用另一个表，怎么可能将其实现到迭代中并正确填充？

But also... if I use another table, how would I possibly be able to implement that into the iteration and populate correctly?

我可以在Meals表中添加一个 qty列，它属于：用户，b

I could add a 'qty' column to the Meals table and make it belong_to :user, but that is also obviously bad practice and will get really messy really quick.

推荐答案

如果要存储类似以下内容的信息：

If you want to store the information something like:




订单包含餐1，餐2和餐3，且订单属于用户1

Order has meal 1, meal 2 and meal 3 and order belongs to User 1

然后，您应该在这3个模型之间具有正确的关联。 用户，膳食和订单

Then you should have the right associations among these 3 models. User, Meal and Order

一个订单可以有很多餐，而一个 Meal 可以属于许多订单，因此 Order 和 Meal 将具有多对多关联。

One Order can have many meals, and one Meal can belong to many orders, So Order and Meal will have many-to-many association.

而订单将属于一个用户

解决方案：

将您的订单模型更改为：

t.belongs_to :user

添加第四个模型，您可以将其命名为 Quantity ：

Add a fourth model, you can name it Quantity:

t.belongs_to :order
t.belongs_to :meal
t.integer :quantity

现在，假设用户A选择了2个单元A，3个单元B，您将为此用户创建一个订单A，订单A在 Quantity 模型中将有两个条目，其中包含餐号及其各自数量的信息。

Now let's say User A, selects 2 units of Meal A, 3 units of Meal B, you will create an order A, for this user, and Order A will have two entries in Quantity model containing the info of meal id and their respective quantities.

更新：
模型将如下所示：

Update: Models will look like this:

Order .rb

Order.rb

belongs_to :user
has_many :quantities
has_many :meals, through: :quantities

Quantity.rb

Quantity.rb

belongs_to :order
belongs_to :meal

Meal.rb

has_many :quantities
has_many :orders, through: :quantities

User.rb

has_many :orders

然后，如果您想获取一顿饭的总订单数，可以通过以下方式获得它：

Then, if you want to get the total number of orders one meal has get, you can get it by:

meal.orders.count

，如果要获得一份订单的所有餐点及其数量：

and if you want to get all the meals one order has and their quantities:

order.quantities.each do |record|
  record.meal.name # for name of associated meal
  record.quantity # for quantity of meal
end

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