active record association: has only one.

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

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 find what you need.

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