How to validate comment in Rails equal to 0 or has length of minimum 10 words

Question

I have a Review Model in Rails which has a rating and a comment. Right now I validate rating, presence true and I don't validate a comment on presence in case users don't want to type a comment. I would like to be able to validate a comment if it's empty. However, if the user decides to type a comment, I would like to validate with length of minimum 10 words.

I found in Rails Guide how to validate length for min or maximum characters. But I have not found how to make a condition:

If it's empty it's ok, If it's not empty, have at least 10 words.

Any help would be greatly appreciated.

Answer 1

validates :comment, length: { minimum: 10 }, :allow_blank => true

Answer 2

I like Ninjarabbi's answer, but it's counting characters, not words.

You can use a custom validation method.

validate :comment_has_enough_words

def comment_has_enough_words
  return if comment.blank?
  errors.add(:comment, "must be at least 10 words") if comment.split.size < 10
end