如何重命名外键？

Question

I want to remove the _id prefix the foreign key?
New table. Two models Order and Product

class Order < ApplicationRecord
  has_many :products
end
class Product < ApplicationRecord
  belongs_to :delivery, :class_name => "Order"
end

Make in the products table t.integer :delivery, index: true

Error:

ActiveRecord::AssociationTypeMismatch: Order(#85313090) expected, got 1 which is an instance of Fixnum(#73138750)

How to fix?

Answer 1

To minimize the possibilities of fighting with rails when doing something like this, I'd simply override the delivery=(value) method. eg:

class Product < ApplicationRecord
  belongs_to :delivery, :class_name => "Order"

  def delivery=(id)
    delivery_id = id
  end
end

In effect, this will prevent assigning objects to the association. Other methods, eg build_delivery and delivery will still be present and could be overwritten as well but as @moveson has already pointed out, striving from the rails way will typically cause pain later on.

Answer 2

You need to specify foreign_key name in models:

class Order < ApplicationRecord
  has_many :products, foreign_key: "delivery"
end

class Product < ApplicationRecord
  belongs_to :delivery, :class_name => "Order", foreign_key: "delivery"
end

Answer 3

The good answer is you don't. You can alias associations by using the foreign key and class_name options:

class Order < ApplicationRecord
  has_many :products, foreign_key: "delivery_id"
end

class Product < ApplicationRecord
  belongs_to :delivery, class_name: "Order"
end

But the _id suffix is a really good convention as it makes very easy to understand the schema as its almost overly apparent which columns are foreign key columns. And conventions are what makes Rails awesome.

There is no good reason to skirt it unless you have a crappy legacy application.