Question

Came across this post & it says referential integrity handled by the DB is not the Rails way at all.

But consider this:

class User < ActiveRecord::Base
  belongs_to :department
end

class Department < ActiveRecord::Base
  has_many :users
end

#User Model
id: integer, name: string,department_id: integer
#Department Model
id: integer, name: string

Here I need to create a new user & enforce following rules

• User should be assigned to a department
• the users.department_id should match departments.id
• if users.department_id doesn’t not match with departments.id, the record should NOT be created & raise an error.

Now, how to I accomplish this in rails way? Or Adding foreign key by dropping raw SQL in a migration is only way to go?

Answer 1

In Rails, you just add this to your User model:

validates_presence_of :department

Rails will check for a valid department before allowing a save operation. You can also use a gem like foreigner to add foreign keys to your tables as well if you desire. I usually do this because I inevitably find myself needing to bulk load data directly at some point.