Question

How can I match a string that is NOT partners?

Here is what I have that matches partners:

/^partners$/i

I’ve tried the following to NOT match partners but doesn’t seem to work:

/^(?!partners)$/i

Answer 1

Your regex

/^(?!partners)$/i

only matches empty lines because you didn’t include the end-of-line anchor in your lookahead assertion. Lookaheads do just that – they “look ahead” without actually matching any characters, so only lines that match the regex ^$ will succeed.

This would work:

/^(?!partners$)/i

This reports a match with any string (or, since we’re in Ruby here, any line in a multi-line string) that’s different from partners. Note that it only matches the empty string at the start of the line. Which is enough for validation purposes, but the match result will be "" (instead of nil which you’d get if the match failed entirely).