NoMethodError: 未定义方法 `<' 为 nil:NilClass

Question

I'm adding a custom validation in my application while creating a coupon, start date of the validity for the coupon should be before the end date.

validate :to_must_be_after_from

private
    def to_must_be_after_from
      if valid_to < valid_from
        self.errors[:base] << "Coupon cannot expire before the start of its validity period."
      end
    end

valid_to and valid_from are the date fields.

---

When I'm running this, NoMethodError occurred. I have the following question regarding this,

1. '<' is an operator and not a function, then how such error can occurs.
2. How to fix this and make the code function properly.

Answer 1

Most operators are actually methods in Ruby. This code:

valid_to < valid_from

is merely syntactic sugar to

valid_to.<(valid_from)

The error message is pretty much self explanatory, you have to make sure valid_to and valid_from are not nil , using guard clause, for example, ie like this:

def to_must_be_after_from
  return if valid_to.blank? || valid_from.blank?

  # rest of the code
end

Answer 2

First you need to check whether valid from or valid to is blank or not. then you can check the value is less than or greater than .

def to_must_be_after_from

  return if valid_from.blank? || valid_to.blank?

  if valid_from < Date.today
    errors.add(:base, "You can't select past dates in valid from")
  elsif valid_to < valid_from
    errors.add(:base, "valid to can't be before the valid from date")
  end
end

Answer 3

Based on the error message-

You are trying to compare variables in which one variable is nil . Can you check if both valid_to and valid_from are having proper values, before checking the validation - if valid_to < valid_from ?