与用户的自我加入关联

Question

I have models: User has_many :orders end; Order belongs_to :user end;

This associations work very well but now i want that User who create order could add another Users for this order.

Edit:

In my orders/show.html.erb i have something like this

<%= form_for @order do |f| %>
<td>
  <%= f.select :user_id, @prac %>
</td>

<% end %> I know this is wrong because i choose here id user who create order, but in this situation i have problem with define correct associations probably this is good idea? =>

order has_many :workes, class_name: 'User'

How can i achieve this functionality?

Answer 1

You can have several relations to the same class, but you probably want to differentiate them (the other Users of your order are probably not the owner). Something like:

class Order < ActiveRecord::Base
  belongs_to: user
  has_many: contributors, , class_name: 'User' # need to specify else Rails will look for a "Contributor" class
end

This will create a one to many relation between the order and a list of Users known as "contributors":

owner = order.user # the initial user
contributors = order.contributors # a list of users related to this order.

Answer 2

You are looking for has_and_belongs_to_many association:

Create join table 'orders_users'

create_table :contributors_orders, :id => false do |t|
  t.integer :contributor_id
  t.integer :user_id
end

Add association:

class Order < ActiveRecord::Base
  belongs_to :user
  has_and_belongs_to_many :contributors, class_name: 'User'
end

And all should work.

Answer 3

Join

You'll need to add another cog into the system - with has_many :through or has_and_belongs_to_many join tables

As Martin mentioned, you'll need to do something like this:

#app/models/user.rb
Class User < ActiveRecord::Base
   has_and_belongs_to_many :orders
end

#app/models/order.rb
Class Order < ActiveRecord::Base
   has_and_belongs_to_many :users
end

#orders_users table
order_id | user_id

This will allow you to set as many users per order as you need - allowing you to call:

@user = User.first
@user.orders


@order = Order.first
@order.users

--

Just noticed this is not self-join . I can refactor if you'd like it to be self-referential