rails validation format regex fails in rubular

Question

I'm adding a validation check on a rails model using the following regex:

validates :reference, :presence => true, :format => { :with => /^[a-zA-Z0-9_. ]*$/i }

This check will match any non alphanumeric chars and ignores underscore and dot.

When testing on rubular.com, the regex fails to match any of the above mentioned patterns. Instead, rubular matches using this regexp:

/[^a-zA-Z0-9_. ]/i

Anyone knows what the reason behind the difference between the two?

Thanks

mu is too short · Accepted Answer · 2012-03-12 22:10:41Z

2

^ has two meanings. When used outside of brackets, it means "line begins with". When used inside brackets, it means that what is matched is the opposite. I feel like I'm not clear so : [a-z] would match every lower case letter, while [^a-z] would match anything but a lower case letter.

edited Mar 12, 2012 at 22:10

mu is too short

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answered Mar 12, 2012 at 21:51

ksol

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4 Comments

mu is too short Over a year ago

You could also say that [^...] negates the character class [...]. I don't know if that's any clearer though.

cnikolaou Over a year ago

I'm not entirely sure that this is the case. Head over to rubular.com and try both: the one with [^...] does match non alpha chars, while the one with ^[..] isn't doing the reverse.

ksol Over a year ago

as @muistooshort said, [^...] negates the character class [...]. ^[...] is not supposed to be the opposite of [^...]. This is one case of ambiguity in regexp syntax, but you'll get used to it. The cheat sheet at the bottom of rubular should help you keep things clear

mu is too short Over a year ago

@cnicolaou: /^[a-z]/ matches anything that begins with 'a' through 'z', /[^a-z]/ matches anything that doesn't contain 'a' through 'z'.

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