Rails validate format with regex

Question

In my rails app, I want to validate input on a string field containing any number of keywords (which could be more than 1 natural language word (e.g. "document number")). To recognize the individual keywords, I am entering them separated by ", " (or get their end by end of string).

For this I use

validates :keywords, presence: true, format: { with: /((\w+\s?-?\w+)(,|\z))/i, message: "please enter keywords in correct format"}

It should allow the attribute keywords (string) to contain: "word1, word2, word3 word4, word5-word6"

It should not allow the use of any other pattern. e.g. not "word1; word2;" It does incorrectly allow "word1; word2"

On rubular, this regex works; yet in my rails app it allows for example "word1; word2" or "word3; word-"

where is my error (got to say am beginner in Ruby and regex)?

There can be whitespace or hyphen in between 1+ word chars, right? — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Nov 11, 2016 at 10:15
yes correct; eg "credit note" or "credit-note" or "credit - note"; but not "credit-" — Dimitri de Ruiter
– Dimitri de Ruiter, Commented Nov 11, 2016 at 10:16
in rubular that works; now in my app it does allows for example "word1; word2" but not "word1; word2;". same as before. — Dimitri de Ruiter
– Dimitri de Ruiter, Commented Nov 11, 2016 at 10:23

Wiktor Stribiżew · Accepted Answer · 2016-11-11 10:29:38Z

17

You need to use anchors \A and \z and modify the pattern to fit that logic as follows:

/\A(\w+(?:[\s-]*\w+)?)(?:,\s*\g<1>)*\z/

See the Rubular demo

Details:

\A - start of string
(\w+(?:[\s-]*\w+)?) - Group 1 capturing:
- \w+ - 1 or more word chars
- (?:[\s-]*\w+)? - 1 or 0 sequences of:
  - [\s-]* - 0+ whitespaces or -
  - \w+ - 1 or more word chars
(?:,\s*\g<1>)* - 0 or more sequences of:
- ,\s* - comma and 0+ whitespaces
- \g<1> - the same pattern as in Group 1
\z - end of string.

answered Nov 11, 2016 at 10:29

Wiktor Stribiżew

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2 Comments

Dimitri de Ruiter Over a year ago

Wiktor, I need to extend the regex to allow "credit note, credit-note, credit note date, credit notes" pattern. i.e. any number of words followed by comma. Have tried now for 2+ hrs but can't find a solution. Help appreciated.

Wiktor Stribiżew Over a year ago

Sorry, there is a national holidary here in Poland, I was offline. I understand you want to match any number of hyphenated/space-separated words that may be followed with 0+ sequence of a comma+space and hyphenated/space-separated words. I think all you need is to replace the ? quantifier in Group 1 with *: \A(\w+(?:[\s-]*\w+)*)(?:,\s*\g<1>)*\z.

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