Active record association: has only one

Hello guys!
I’m new on RoR. I’m testing an application for married person using this

The goal is:

  • A sign-in person can only get only one follower ( his wife or husband)

Where should i modified this app for this features?
Thanks for your help!

Go to Active Record Associations — Ruby on Rails Guides and you’ll
what you need.

As a side note, you should bookmark and
familiar with its’ contents.