How to generate a model with has_one contraint

Question

I want to create 2 models, where one belongs to another. I know the generate command to create a model that “belongs_to” another but I have no clue how to have the other model have “has_one”.

Can I specify “has_one” in the generate command? Or do I manually add it to the model file after?

This still confuses me since the child that “belongs_to” has the foreign key and the parent that “has_one” doesn’t have anything.

And isn’t this a one-to-one relationship, and so not needed?

Answer 1

Let's use some concrete terms for examples. We'll say a user has one profile.

To generate the user and profile, you could use:

rails generate model User email:string username:string
rails generate model Profile user:references about_me:text

So yes, you do have to add the line has_one :profile to the user model. No, you don't have to add the line belongs_to :user to the profile model as this will be added for you.

As for your last question, I'm not sure what you mean. Yes, this is a one-to-one relationship, but what part do you think is not needed? The has_one :profile line?

If that's the part you're not understanding, you're not fully understanding what this line gives you. It adds useful methods to the User class, most important of which are probably @user.build_profile and @user.profile. Might not seem like much, but pretty cool for adding just one line of code imho.