CString to string problem

[patil_ruturaj]

Hi,

I m using a dll call to play a wav file .
It is like this Playfile("c:\temp\chimes.wav",2);

now i have used GetPathName property to get the path name of the selected file into the CString m_iResults.

Now if i use the syntax as Playfile(m_iResults,2); it gives me error saying - cannot convert parameter 1 from 'class CString' to 'char *'
No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called


please provide me the solution or a way to solve this problem.

rutu.

[tmecham]

See if Playfile(m_iResults.GetString(),2) works for you.

[Joe Nellis]

Playfile((LPCTSTR)m_iResults,2);

[vicodin451]

Originally posted by patil_ruturaj
Hi,

I m using a dll call to play a wav file .
It is like this Playfile("c:\temp\chimes.wav",2);

now i have used GetPathName property to get the path name of the selected file into the CString m_iResults.

Now if i use the syntax as Playfile(m_iResults,2); it gives me error saying - cannot convert parameter 1 from 'class CString' to 'char *'
No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called


please provide me the solution or a way to solve this problem.

rutu.

You cannot "convert" a CString to a char*. A const char*, yes, but a char* - no. You can copy from a CString to a char buffer. You can also use GetBuffer/ReleaseBuffer, but I personally avoid these.

See if Playfile(m_iResults.GetString(),2) works for you.

This will not work. GetString returns a const PCXSTR. Plus, the method is not available in MFC42 / MSVC 6.0.

Playfile((LPCTSTR)m_iResults,2);

This will not work. The Playfile function requires a char*. Explicitly casting it to a const pointer will not cause it to behave any differently since CString has an operator LPCTSTR that allows for implicit casts.

Here's what I would do:

/* Contains filename to pass to Playfile, presumably obtained by calling CFileDialog::GetPathName */
CString m_iResults; 

char szFileToPlay[MAX_PATH + 1] = {0};
strncpy( szFileToPlay, m_iResults, MAX_PATH );
Playfile( szFileToPlay, 2 );

[csheng]

I use this all the time.

CString cs;
(LPCTSTR)cs.GetBuffer(cs.GetLength());
cs.ReleaseBuffer();

Is there any issue with this code so you avoid it?

csheng

[tmecham]

Funny, this compiles just fine in my project:

CString sound("C:\\sound.wav");
::PlaySound(sound.GetString(),0,SND_ASYNC);

*shrugs*

[vicodin451]

Originally posted by tmecham
Funny, this compiles just fine in my project:

CString sound("C:\\sound.wav");
::PlaySound(sound.GetString(),0,SND_ASYNC);

*shrugs*

Ummm..
1) You're apparently using VC++ 7.x/MFC7x. CString::GetString does not exist in VC++ 6.0/MFC4.2. Plus, you don't even need to call GetString for PlaySound. See #2.
2) You are calling PlaySound, not Playfile.
PlaySound, from MSDN:

BOOL PlaySound(
  LPCSTR pszSound,  
  HMODULE hmod,     
  DWORD fdwSound    
);

Note that the first param is a LPCSTR (const char*), not a char*. Playfile is obviously a different function, especially since the compiler says the first param should be a char*.

[vicodin451]

Originally posted by csheng
I use this all the time.

CString cs;
(LPCTSTR)cs.GetBuffer(cs.GetLength());
cs.ReleaseBuffer();

Is there any issue with this code so you avoid it?

csheng

Why would you do such a thing? You are using a function to retrieve the (non-const) pointer to the internal char buffer, and then casting it to a const pointer. CString has an implicit LPCTSTR conversion operator - "use" that instead. It's more intuitive and makes the code more readable.

I avoid GetBuffer/ReleaseBuffer because I don't like the idea of messing with the internal buffer that's managed by the CString object. Seems like a hack. I know how to use the functions and what they are provided for, but choose not to use them. I've seen use of GetBuffer abused far too many times...

[maggiemay]

CEdit * pedit = (CEdit*)GetDlgItem(IDC_EDIT_SOUND);
pedit->GetWindowText(m_sWaveFileToPlay);
sndPlaySound(NULL, SND_SYNC);
sndPlaySound(m_sWaveFileToPlay, SND_SYNC);

[patil_ruturaj]

Hi,

Thanks to all !
Since all of you had intension to help me i tried every suggestion given by you.But the solution given by vicodin451

--------------------------------------------------------------------------------
char szFileToPlay[MAX_PATH + 1] = {0};
strncpy( szFileToPlay, m_iResults, MAX_PATH );
Playfile( szFileToPlay, 2 );
--------------------------------------------------------------------------------

worked fine and was easy.Yes i use VC6.

Thanks again.Hope it continues.
Rutu.

[gstercken]

Just another thought: Where does this Playfile() function come from? Did you provide it? If yes, then note that you should rather change the first parameter to a const char* (or LPCTSTR, for that matter) instead of a char*. After all, Playfile() doesn't seem to modify the string you pass, so why should you make that parameter non-const?

[csheng]

Good point.

If wanted to get char * from cstring and gettin getting the internal buffer from cstring is not such a bad thing, at least not for me,
casting it to const is also logical as PlayFile won't change it anyways.

csheng