Error in displayin in MsgBox

[balajee]

Hi

I am trying to read a text file by each character and displaying the character read in a message box. I have included these header files: fstream.h and conio.h.

Following is the code I am using. But when run this code I get error at the line "MessageBox(ch);"

Error:
"Conversion from integral type to pointer type requires reinterpret_cast, C-style cast or function-style cast"

Code:

{
char ch;
ifstream file;

file.open("test.txt",ios::nocreate);

if(!file)

{

MessageBox("UNABLE TO OPEN FILE!!"

goto end;

}

while(file)

{

file.get(ch);
MessageBox(ch);

}

getch();

end:

file.close();

Thanks,

 

[bcravens]

Sounds to me like C++ is interpreting the char variable as a number (byte) and that MessageBox takes a string as in parameter.

I verified that this is so in my environment. Additionally the following code worked for me. I simply defined char to be a pointer intead.



#include "stdafx.h"
#include "windows.h"

int main(int argc, char* argv[])
{
char *ch2;
ch2 = "a";
MessageBox(NULL,ch2,"Title",MB_OK);
return 0;
}


Hope this gets you closer to your answer!

 

[balajee]

Thanks for the reply. I tried your suggestion declaring the line "char ch;" as "char *ch;", but now I get the following error at line "file.get(ch);"

class istream &__thiscall istream::get(char &)' : cannot convert parameter 1 from 'char *' to 'char &'
A reference that is not to 'const' cannot be bound to a non-lvalue

Please help,

Thanks

 

[bcravens]

It would help if you could copy all of your code and paste it. That way I can see exactly the message on my machine.

Thanks.

 

[balajee]

Hi
I have created a simple MFC Appwizard(exe) project using the defaults settings. I am attaching the code to the click event of "OK" button.

I am attaching herewith the code which is trying to read and display a text file which has just one line.

Code Starts here:

// TestingFileReadingDlg.cpp : implementation file
//

#include "stdafx.h"
#include "TestingFileReading.h"
#include "TestingFileReadingDlg.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// CAboutDlg dialog used for App About

class CAboutDlg : public CDialog
{
public:
CAboutDlg();

// Dialog Data
//{{AFX_DATA(CAboutDlg)
enum { IDD = IDD_ABOUTBOX };
//}}AFX_DATA

// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CAboutDlg)
protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
//}}AFX_VIRTUAL

// Implementation
protected:
//{{AFX_MSG(CAboutDlg)
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};

CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
//{{AFX_DATA_INIT(CAboutDlg)
//}}AFX_DATA_INIT
}

void CAboutDlg:oDataExchange(CDataExchange* pDX)
{
CDialog:oDataExchange(pDX);
//{{AFX_DATA_MAP(CAboutDlg)
//}}AFX_DATA_MAP
}

BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
//{{AFX_MSG_MAP(CAboutDlg)
// No message handlers
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CTestingFileReadingDlg dialog

CTestingFileReadingDlg::CTestingFileReadingDlg(CWnd* pParent /*=NULL*/)
: CDialog(CTestingFileReadingDlg::IDD, pParent)
{
//{{AFX_DATA_INIT(CTestingFileReadingDlg)
// NOTE: the ClassWizard will add member initialization here
//}}AFX_DATA_INIT
// Note that LoadIcon does not require a subsequent DestroyIcon in Win32
m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}

void CTestingFileReadingDlg:oDataExchange(CDataExchange* pDX)
{
CDialog:oDataExchange(pDX);
//{{AFX_DATA_MAP(CTestingFileReadingDlg)
// NOTE: the ClassWizard will add DDX and DDV calls here
//}}AFX_DATA_MAP
}

BEGIN_MESSAGE_MAP(CTestingFileReadingDlg, CDialog)
//{{AFX_MSG_MAP(CTestingFileReadingDlg)
ON_WM_SYSCOMMAND()
ON_WM_PAINT()
ON_WM_QUERYDRAGICON()
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CTestingFileReadingDlg message handlers

BOOL CTestingFileReadingDlg::OnInitDialog()
{
CDialog::OnInitDialog();

// Add "About..." menu item to system menu.

// IDM_ABOUTBOX must be in the system command range.
ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
ASSERT(IDM_ABOUTBOX < 0xF000);

CMenu* pSysMenu = GetSystemMenu(FALSE);
if (pSysMenu != NULL)
{
CString strAboutMenu;
strAboutMenu.LoadString(IDS_ABOUTBOX);
if (!strAboutMenu.IsEmpty())
{
pSysMenu->AppendMenu(MF_SEPARATOR);
pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
}
}

// Set the icon for this dialog. The framework does this automatically
// when the application's main window is not a dialog
SetIcon(m_hIcon, TRUE); // Set big icon
SetIcon(m_hIcon, FALSE); // Set small icon

// TODO: Add extra initialization here

return TRUE; // return TRUE unless you set the focus to a control
}

void CTestingFileReadingDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
if ((nID & 0xFFF0) == IDM_ABOUTBOX)
{
CAboutDlg dlgAbout;
dlgAbout.DoModal();
}
else
{
CDialog::OnSysCommand(nID, lParam);
}
}

// If you add a minimize button to your dialog, you will need the code below
// to draw the icon. For MFC applications using the document/view model,
// this is automatically done for you by the framework.

void CTestingFileReadingDlg::OnPaint()
{
if (IsIconic())
{
CPaintDC dc(this); // device context for painting

SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);

// Center icon in client rectangle
int cxIcon = GetSystemMetrics(SM_CXICON);
int cyIcon = GetSystemMetrics(SM_CYICON);
CRect rect;
GetClientRect(&rect);
int x = (rect.Width() - cxIcon + 1) / 2;
int y = (rect.Height() - cyIcon + 1) / 2;

// Draw the icon
dc.DrawIcon(x, y, m_hIcon);
}
else
{
CDialog::OnPaint();
}
}

// The system calls this to obtain the cursor to display while the user drags
// the minimized window.
HCURSOR CTestingFileReadingDlg::OnQueryDragIcon()
{
return (HCURSOR) m_hIcon;
}

#include <string.h>
#include <fstream.h>
#include <conio.h>
#include &quot;windows.h&quot;

void CTestingFileReadingDlg::OnOK()
{
char *ch2;

ifstream file;

file.open(&quot;test.txt&quot;,ios::nocreate);

if(!file)

{

MessageBox(&quot;UNABLE TO OPEN FILE!!&quot;

goto end;

}

while(file)

{

file.get(ch2);

MessageBox(ch2);

}

getch();

end:

file.close();


CDialog::OnOK();
}


Code ends here.

The code after the line &quot;void CTestingFileReadingDlg::OnOK()&quot; is the code I have added including the few header files above this. Rest is created by the wizard.

hope this is makes sense,

thanks

 

[bcravens]

I have redone my example using a file for input. Create the file and place in the same directory that you are running the compiled app from.




#include &quot;stdafx.h&quot;
#include &quot;windows.h&quot;
#include <stdio.h>
#include <conio.h>

int main(int argc, char* argv[])
{
char ch[2];
char *chOut;
FILE *fp;
ch[1] = '\0';
if((fp = fopen(&quot;textIn.txt&quot;,&quot;r&quot) != NULL)
{

while(fread(&ch,sizeof(char),1,fp)>0)
{
MessageBox(NULL,ch,&quot;Title&quot;,MB_OK);
}

fclose(fp);

}
else
{
MessageBox(NULL,&quot;Could not find file 'textIn.text'!&quot;,&quot;File Not Found&quot;,MB_OK);
getch();
}

return 0;
}



MessageBox takes a null terminated string as its input. So I after reading in a character from a file you must place a terminating '\0' at the end for it to be a valid string.


Hope this helps.

 

[balajee]

Hi

I am sorry I could not understand your suggestion of using pointer variable. Now I have used it correctly and there is no error. But the character displayed has some funny characters attached at the end. How do I get rid off these?

Once again sorry for this,

Thanks

 

[balajee]

OK. Got that. Thank you very much.