Validating that a record in a related table exists

Rails
1

Hi, I’m fairly new to Ruby and Rails. I’m trying to get my models
validating and I’ve run into a problem.

I’ve got two models User and Contact. User belongs_to contact and
contact has_one user.

A Contact can exist without a User, however a User cannot exist without
a corresponding Contact.

Also, the Contact model contains an email address. This email address
can be null, but if there is a User corresponding with the Contact then
there must be an email address.

So basically, upon creating a user I need to check that (a) the
contact_id of the user exists in Contacts, and (b) that the email field
of the corresponding Contact is not blank.

Is there a special Rails way of doing this (particularly part a), or do
I need to create my own validation code (which I assume will be the case
for part b no matter what)?

Also, am I right in assuming that if I use contact.email within an
instance of my User class it will pick out the corresponding Contact for
said User?

Thanks for any help or pointers!

2

Okay, I think I’ve got it:

I’ve put in the User model “validates_presence_of :contact” to ensure
that the contact actually exists.

I’ve then added the following validates method:

def validate
if contact && contact.email.nil?
errors.add(‘email’, ‘Related contact must have email’)
end
end

Testing seems to work so I think it’s right!