生成随机guid串的代码

NSString *  result;

    CFUUIDRef   uuid;

    CFStringRef uuidStr;

    

    uuid = CFUUIDCreate(NULL);

    assert(uuid != NULL);

    

    uuidStr = CFUUIDCreateString(NULL, uuid);

    assert(uuidStr != NULL);

    

    result = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSStringstringWithFormat:@"%@-%@", prefix, uuidStr]];

    assert(result != nil);

    

    CFRelease(uuidStr);

    CFRelease(uuid);

    

    return result;