What's the difference between belongs_to and has_one?

Question

What is the difference between a belongs_to and a has_one?

Reading the Ruby on Rails guide hasn\'t helped me.

Answer 1

From a simplicity standpoint, belongs_to is better than has_one because in has_one, you would have to add the following constraints to the model and table that has the foreign key to enforce the has_one relationship:

• validates :foreign_key, presence: true, uniqueness: true
• add a database unique index on the foreign key.