try :
CFUUIDRef udid = CFUUIDCreate(NULL);
NSString *udidString = (NSString *) CFUUIDCreateString(NULL, udid);
UPDATE:
从iOS 6there is an easier way to generate UUID开始.和往常一样，有多种方法可以做到这一点:
创建UUID字符串:
NSString *uuid = [[NSUUID UUID] UUIDString];
创建UUID:
[NSUUID UUID]; // which is the same as..
[[NSUUID] alloc] init];
创建一个类型为NSConcreteUUID的对象，可以轻松地强制转换为NSString，如下所示:BE5BA3D0-971C-4418-9ECF-E2D1ABCB66BE
NOTE from the Documentation:个
Note: NSUUID类与CoreFoundation的CFUUIDRef不是免费桥接的.如果需要，使用UUID字符串在CFUUID和NSUUID之间进行转换.不能保证两个NSUUID对象在指针值上具有可比性(就像CFUUIDRef一样)；使用isEquity:比较两个NSUUID实例.