Check whether an attribute of a model exists

Question

In Rails, I am getting an error when I try to evaluate whether the user has entered a brand for their computer:

if @user.computer.brand.empty?

NoMethodError (undefined method 'brand' for nil:NilClass):

If the user has not entered a computer, this will return an error that there is no method brand on nil class. What is the correct way to check that a user has both entered a computer and a brand for that computer?

Answer 1

Try with try:

@user.computer.try(:brand)

This will return nil if either computer or computer.brand is nil, or it will return the assigned brand.

Answer 2

if @user.computer && @user.computer.brand.present?

Answer 3

if @user.computer.present? && @user.computer.brand.present? 

You can also use ! nil? instead of present.

See this post - very useful