UUID Strings with Cocoa

PUBLISHED ON OCT 25, 2012

This used to be a thing until the iOS 6 and OS X 10.8 compatible NSUUID Class became available.

New

This is how you can do it now:

NSString *uuidString = [[NSUUID UUID] UUIDString];
// Generates: 7E60066C-C7F3-438A-95B1-DDE8634E1072

Old

Here’s a method you can put in a class, with the correct ARC casts on ownership, that returns a UUID. It’s a fairly common technique, and you’ll even see versions of it where people have created a category on NSString for this.

- (NSString *)uuidString {
    // Returns a UUID

    CFUUIDRef uuid = CFUUIDCreate(kCFAllocatorDefault);
    NSString *uuidStr = (__bridge_transfer NSString *)CFUUIDCreateString(kCFAllocatorDefault, uuid);
    CFRelease(uuid);

    return uuidStr;
}

And to use it:

NSString *uuidString = [self uuidString];
// Generates D5CB0560-206F-4581-AA25-1D6A873F3526

NSProcessInfo

A common use for unique strings is to name files and directories within a program so that they do not clash. Since iOS 2 and OS X 10.0 there has been the globallyUniqueString method in NSProcessInfo which returns a string that is unique for the network and process. So, for a good enough unique string this is probably a better method to use:

NSString *uuidStr = [[NSProcessInfo processInfo] globallyUniqueString];
// generates 56341C6E-35A7-4C97-9C5E-7AC79673EAB2-539-000001F95B327819