error C2065: 'nocreate' : undeclared identifier

 

 

In addition to the above changes, the following functions, constants, and enumerators that are elements of the old iostream library are not elements of the new iostream library:

• attach member function of filebuf, fstream ifstream, and ofstream
• fd member function of filebuf, fstream ifstream, and ofstream
• filebuf::openprot
• filebuf::setmode
• ios::bitalloc
• ios::nocreate
• ios::noreplace
• ios::sync_with_stdio
• streambuf::out_waiting
• streambuf::setbuf (use rdbuf -> pubsetbuf for the same behavior)

what's the .net replacement for ios::nocreate

"John Harrison" <> wrote in message news:<>...

> > In the new VC++ 7.0 ios::nocreate is obsolete. Does any one know what
> > I should do to achieve the same goal? I really want to check if a
> > file exists before reading from it.
> >

>
> There is no need for nocreate. If you open a file for reading and the file
> doesn't exist, then the open will fail. Nocreate is the default if you like.

所以不用nocreate也是可以的

在C++中

#include <fstream>
#include <iostream>
using namespace std;

使用ios::nocreate会报告错误：

error C2039: 'nocreate' : is not a member of 'basic_ios<char,struct std::char_traits<char> >'
error C2065: 'nocreate' : undeclared identifier
执行 cl.exe 时出错.

 

在C中

#include<fstream.h>  

#include<stdlib.h>

可以直接使用

原因在于

ios::nocreate是在C++标准制定之前在<fstream.h>中有定义的。但是因为它跟系统平台相关密切，所以在C++标准中去掉了对它的支持。