IOS生成UUID

/**
 * 生成GUID
 */
+ (NSString *)generateUuidString{
    // create a new UUID which you own
    CFUUIDRef uuid = CFUUIDCreate(kCFAllocatorDefault);
    
    // create a new CFStringRef (toll-free bridged to NSString)
    // that you own
    NSString *uuidString = (NSString *)CFUUIDCreateString(kCFAllocatorDefault, uuid);
    
    // transfer ownership of the string
    // to the autorelease pool
    [uuidString autorelease];
    
    // release the UUID
    CFRelease(uuid);
    
    return uuidString;
}
@end