Validate attribute's length if present

Question

How to make validation where presence of model's attribute isn't necessary, but if it is present, attribute's length must be more than three characters?

Listed

What is your Rails version? – Wifely

4.2.0, why do you ask? – Listed

example with unless: has a different syntax in Rails version < 4 – Wifely

Answer 1

You can allow attribute to be blank with allow_blank: true or nil with allow_nil: true and also check the length: :

validates :attr, length: { minimum: 4 }, allow_blank: true
validates :attr, length: { minimum: 4 }, allow_nil: true

You can also use if: or unless: :

validates :attr, length: {minimum: 4}, unless: -> (item) { item.blank? }

Wifely