如何动态分配 CFile 类型的变量？ （C++，CFile，新）

Question

static TCHAR BASED_CODE szFilter[] = _T("YUV Files|*.yuv|")
CFileDialog fileDlg(TRUE, _T("yuv"), _T("bus.yuv"), OFN_FILEMUSTEXIST | OFN_HIDEREADONLY, szFilter);
if (fileDlg.DoModal() == IDOK)
{
    CString pathName = fileDlg.GetPathName();
    CFile* pImgFile = NULL;
    pImgFile = new CFile(pathName, CFile::modeRead || CFile::typeBinary);
}

I refer to an example in the following site. https://msdn.microsoft.com/en-us/library/b569d0t4.aspx

static TCHAR BASED_CODE szFilter[] = _T("YUV Files|*.yuv|")
CFileDialog fileDlg(TRUE, _T("yuv"), _T("bus.yuv"), OFN_FILEMUSTEXIST | OFN_HIDEREADONLY, szFilter);
if (fileDlg.DoModal() == IDOK)
{
    CString pathName = fileDlg.GetPathName();
    CFile imgFile;
    CFileException e;
    if (!imgFile.Open(pathName, CFile::modeRead || CFile::typeBinary, &e))
    {
        TRACE(_T("File could not be opened %d\n"), e.m_cause);
    }
}

I refer to the first example in the following site. https://msdn.microsoft.com/en-us/library/hwbccf8z.aspx

---

I used the method of CFile, Open, in the second code.

For the upper code, how can I open the file?

When I use dynamic allocation, is it automatically open the file?

imgLength = pImgFile->GetLength();
CString str;
str.Format(_T("Your SYSTEM.INI file is %I64u bytes long."), imgLength);
AfxMessageBox(str); 

I tried to append this code to the first code.

It works without any problems, and I think the variable, pImgFile, points the address of the file well.

Answer 1

In general there is no need to create a CFile on the heap. There are several constructors of CFile :

CFile( );
CFile(
   CAtlTransactionManager* pTM
);
CFile(
   HANDLE hFile 
);
CFile(
   LPCTSTR lpszFileName,
   UINT nOpenFlags 
);
CFile(
   LPCTSTR lpszFileName,
   UINT nOpenFlags,
   CAtlTransactionManager* pTM
);

The fourth and the fifth constructors call Open internally. So they do open the file.

The other problem is that you should use operator | not || to combine open flags.

I'd suggest using the default CFile constructor and then call Open . Please note that it wont throw an exception in case of error (returns FALSE instead) and you wont need to place try/catch around it. Optionally you can also pass CFileException* to Open to get more information if it fails.