Question

I wanted to validate ‘numericality’ of a string (its not an attribute in an active-record model). I just need it to be a valid base 10, positive integer string. I am doing this:

class String
  def numeric?
    # Check if every character is a digit
    !!self.match(/\A[0-9]+\Z/)
  end
end

class String
  def numeric?
    # Check is there is *any* non-numeric character
    !self.match(/[^0-9]/)
  end
end

Which of these is a more plausible alternative? OR, is there any other better implementation?

Answer 1

Please make sure use \A and \Z rather than ^ and $, to match the entire string rather than just a single line in the string. If you want to avoid matching a string with an ending newline, use ‘\z’ at the end. For more issues, see The Regex Tutorial on anchors.

For example, /^[0-9]+$/ successfully matches the following:

foo
1234
bar

but /\A[0-9]+\Z/ does not.