Question

I have this custom validations that throws an “undefined method `>’ for nil:NilClass” when ever birthday is not set because birthday is nil.

validate :is_21_or_older 
def is_21_or_older
  if birthday > 21.years.ago.to_date
    errors.add(:birthday, "Must 21 Or Older")
  end
end

I already have validates_presence_of for birthday so is there a way to have is_21_or_older called only after validates_presence_of passes?

Answer 1

Rails runs all validators independently, in order to give you an array of all the errors at once. This is done to avoid the all too common scenario:

Please enter a password.

pass

The password you have entered is invalid: it does not contain a number.

1234

The password you have entered is invalid: it does not contain a letter.

a1234

The password you have entered is invalid: it is not at least six characters long.

ab1234

The password you have entered is invalid: you cannot use three or more consecutive characters in a sequence.

piss off

The password you have entered is invalid: it does not contain a number.

There are two things you can do, that I know of. Either include everything under your custom validator, in which case everything is under your control, or use the :unless => Proc.new { |x| x.birthday.nil? } modifier to explicitly restrict your validator from running under the circumstances it would break. I’d definitely suggest the first approach; the second is hacky.

def is_21_or_older
  if birthday.blank?
    errors.add(:birthday, "Must have birthday")
  elsif birthday > 21.years.ago.to_date
    errors.add(:birthday, "Must 21 Or Older")
  end
end

Maybe an even better approach is to keep the presence validator, just exit your custom validator when it sees the other validator’s condition is failed.

def is_21_or_older
  return true if birthday.blank? # let the other validator handle it

  if birthday > 21.years.ago.to_date
    errors.add(:birthday, "Must 21 Or Older")
  end
end