Ruby On Rails One-One relationship On Same Table

Question

In my rails application I have a table with the following columns (table name categories)

• id
• title
• summary
• parent_id

How do I setup the relationship so I can do something like @category.parent.title?

Answer 1

Use the acts_as_tree gem?

More info here.

Answer 2

belongs_to :category, :foreign_key => :parent_id
has_many :categories, :foreign_key => :parent_id

Note that if a category has no parent category and you try to access it anyway, you get an error.