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Editorial Team
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Asked: 2026-05-19T01:42:09+00:00

I’m working on an iOS Cocoa app that has a fallback – if the

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I’m working on an iOS Cocoa app that has a fallback – if the user doesn’t enter a certain piece of data, the device’s UDID is used instead, as a default. I need to add a check in our server code (written in Ruby) to recognize whether the value being sent up is a UDID (the user’s default) or a custom string that they’ve set.

It seems that the right solution to my problem is a regular expression. I’m comfortable writing regex’es, but I need to be certain that this regex is 100% guaranteed to recognize a UDID.

I retrieve the UDID in code using:

[[UIDevice currentDevice] uniqueIdentifier]

And in the simulator, I get back this value:

6938CA7D-ECE2-53A4-B293-961A8D07AFB1

From this I might infer that I can just search for a string of hex characters that matches the pattern 8-4-4-4-12. But I want to be certain this works for every UDID.

I can’t find anything about this in Apple’s documentation and was wondering if anyone could give me a definitive answer to this question… thanks!

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1 Answer

  1. Editorial Team

    Why not send another bit of data indicating that it is a UDID? Or just use a different parameter name (UDID=6938...).

    Then, in your server, you can test it like so if you really want to:

    # somewhere outside the controller action, maybe the top of the file
UDID_PATTERN = /\A[a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{12}\Z/

# inside the controller action you're sending info to
udid = params[:UDID]
if udid && (udid =~ UDID_PATTERN)
  # do something with the UDID in place of the other
  # bit of info they could have provided
end
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