Rails 5: Database design with iterations

问题

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

Users table holds the User information
Meals table holds the Meal name, description, img(url)

I am currently displaying the Meals using an iteration:

<% @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 %>

Orders table holds the qty's that the user wants for each Meal

Orders migration for reference:

  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..

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

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?

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

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.

回答1:

If you want to store the information something like:

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

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

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

And an Order will belong to a User

Solution:

Change your Order model to:

t.belongs_to :user

Add a fourth model, you can name it Quantity:

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

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.

Update: Models will look like this:

Order.rb

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

Quantity.rb

belongs_to :order
belongs_to :meal

Meal.rb

has_many :quantities
has_many :orders, through: :quantities

User.rb

has_many :orders

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

meal.orders.count

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

来源：https://stackoverflow.com/questions/53016976/rails-5-database-design-with-iterations

标签

ruby-on-rails

database-design

relational-database