To check a user input english name is valid, I would usually match the input against regular expression such as [A-Za-z]. But how can I do this if multi-language(like Chinese, Japanese etc.) support is required with utf8 encoding?
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What language/regular expression implementation do you use?Gumbo– Gumbo2010-12-01 10:33:42 +00:00Commented Dec 1, 2010 at 10:33
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Ideally support all languages, is that possible?Hongbo– Hongbo2010-12-01 10:35:27 +00:00Commented Dec 1, 2010 at 10:35
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I think Gumbo means "what programming language are you using?"Tim Pietzcker– Tim Pietzcker2010-12-01 13:11:44 +00:00Commented Dec 1, 2010 at 13:11
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2Read this.Tim Pietzcker– Tim Pietzcker2010-12-01 13:15:36 +00:00Commented Dec 1, 2010 at 13:15
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3 Answers
You can approximate the Unicode derived property \p{Alphabetic} pretty succintly with [\pL\pM\p{Nl}] if your language doensn’t support a proper Alphabetic property directly.
Don’t use Java’s \p{Alpha}, because that’s ASCII-only.
But then you’ll notice that you’ve failed to account for dashes (\p{Pd} or DashPunctuation works, but that does not include most of the hyphens!), apostrophes (usually but not always one of U+27, U+2BC, U+2019, or U+FF07), comma, or full stop/period.
You probably had better include \p{Pc} ConnectorPunctuation, just in case.
If you have the Unicode derived property \p{Diacritic}, you should use that, too, because it includes things like the mid-dot needed for geminated L’s in Catalan and the non-combining forms of diacritic marks which people sometimes use.
But then you’ll find people who use ordinal numbers in their names in ways that \p{Nl} (LetterNumber) doesn’t accomodate, so you throw \p{Nd} (DecimalNumber) or even all of \pN (Number) into the mix.
Then you realize that Asian names often require the use of ZWJ or ZWNJ to be written correctly in their scripts, so then you have to add U+200D and U+200C to the mix, which are both \p{Cf} (Format) characters and indeed also JoinControl ones.
By the time you’re done looking up the various Unicode properties for the various and many exotic characters that keep cropping up — or when you think you’re done, rather — you’re almost certain to conclude that you would do a much better job at this if you simply allowed them to use whatever Unicode characters for their name that they wish, as the link Tim cites advises. Yes, you’ll get a few jokers putting in things like “əɯɐuʇƨɐ⅂ əɯɐuʇƨɹᴉℲ”, but that just goes with the territory, and you can’t preclude silly names in any reasonable way.
1 Comment
Jonathan Arkell
I don't know what I like more about this answer more: the fact that it actually does answer the question, the fact that it potentially teaches a lot about unicode regular expressions in general, or the fact that it succinctly demonstrates why trying to validate real names is a bad idea.
Think about whether you really need to validate the user's name. Maybe you should let users call themselves whatever they want.
You certainly should never use [A-Za-z], because some people have names with apostrophes or hyphens. It can be quite insulting to prevent someone from using their real name just because it doesn't follow your arbitrary rules for what a name should look like.
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In PHP I use this nasty hack:
setlocale(LC_ALL, 'de_DE');
preg_match('/^[[:alpha:]]+$/', $name);
That includes "Umlauts" (i.e. 'ä','ö' and the like) plus accented vowels (è,í,etc.). But it falls short to validate for Cyrillic (Russia, Bulgaria, ...) or Chinese characters...
