Conversion Char To Char * Problem

This is a discussion on Conversion Char To Char * Problem within the Windows Programming forums, part of the Platform Specific Boards category; I recently make a Win32 program using MFC. I am using Visual C++ 6.0. The program suppose to run a ...

  1. #1
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    Conversion Char To Char * Problem

    I recently make a Win32 program using MFC. I am using Visual C++ 6.0. The program suppose to run a dialog box that will perform a calculation. I get an error that say I must cast from char to char *. Here is the code:

    Code:
    #include <afxwin.h>
    #include "Addition_ids.h"
    #include "CAdditionDialog.h"
    
    afx_msg void CAdditionDialog::OnAdd()
    {
    	const int TEXT_SIZE = 16;
    	char szText(TEXT_SIZE + 1);
    	CEdit *pTotal = (CEdit *)(GetDlgItem(IDC_TOTAL));
    	CEdit *pNum = (CEdit *)(GetDlgItem(IDC_NUMBER));
    
    	pNum->GetWindowText(szText, TEXT_SIZE);
    	m_nTotal += atoi(szText);
    	itoa(m_nTotal, szText, 10);
    	pTotal->SetWindowText(szText);
    	pNum->SetWindowText("");
    	pNum->SetFocus();
    }
    
    afx_msg void CAdditionDialog::OnClear()
    {
    	CEdit *pTotal = (CEdit *)(GetDlgItem(IDC_TOTAL));
    	CEdit *pNum = (CEdit *)(GetDlgItem(IDC_NUMBER));
    
    	m_nTotal = 0;
    	pTotal->SetWindowText("");
    	pNum->SetFocus();
    }
    
    BEGIN_MESSAGE_MAP(CAdditionDialog, CDialog)
       ON_COMMAND(IDC_ADD, OnAdd)
       ON_COMMAND(IDC_CLEAR, OnClear)
    END_MESSAGE_MAP()
    
    class CAdditionApp : public CWinApp
    {
    public:
    	BOOL InitInstance()
    	{
    		CAdditionDialog addition_dialog;
    
    		addition_dialog.DoModal();
    		return FALSE;
    	}
    } additionApp;
    Here the error I get:

    Code:
    D:\VS 6.0 Test\testexperiment7\Addition.cpp(12) : error C2664: 'int __thiscall CWnd::GetWindowTextA(char *,int) const' : cannot convert parameter 1 from 'char' to 'char *'
            Conversion from integral type to pointer type requires reinterpret_cast, C-style cast or function-style cast
    D:\VS 6.0 Test\testexperiment7\Addition.cpp(13) : error C2664: 'atoi' : cannot convert parameter 1 from 'char' to 'const char *'
            Conversion from integral type to pointer type requires reinterpret_cast, C-style cast or function-style cast
    D:\VS 6.0 Test\testexperiment7\Addition.cpp(14) : error C2664: 'itoa' : cannot convert parameter 2 from 'char' to 'char *'
            Conversion from integral type to pointer type requires reinterpret_cast, C-style cast or function-style cast
    D:\VS 6.0 Test\testexperiment7\Addition.cpp(15) : error C2664: 'SetWindowTextA' : cannot convert parameter 1 from 'char' to 'const char *'
            Conversion from integral type to pointer type requires reinterpret_cast, C-style cast or function-style cast
    I have try the following solution:

    Code:
    #include <afxwin.h>
    #include "Addition_ids.h"
    #include "CAdditionDialog.h"
    
    afx_msg void CAdditionDialog::OnAdd()
    {
    	const int TEXT_SIZE = 16;
    	char szText(TEXT_SIZE + 1);
    	CEdit *pTotal = (CEdit *)(GetDlgItem(IDC_TOTAL));
    	CEdit *pNum = (CEdit *)(GetDlgItem(IDC_NUMBER));
    
    	pNum->GetWindowText((char *)szText, TEXT_SIZE);
    	m_nTotal += atoi((char *)szText);
    	itoa(m_nTotal, (char *)szText, 10);
    	pTotal->SetWindowText((char *)szText);
    	pNum->SetWindowText("");
    	pNum->SetFocus();
    }
    
    afx_msg void CAdditionDialog::OnClear()
    {
    	CEdit *pTotal = (CEdit *)(GetDlgItem(IDC_TOTAL));
    	CEdit *pNum = (CEdit *)(GetDlgItem(IDC_NUMBER));
    
    	m_nTotal = 0;
    	pTotal->SetWindowText("");
    	pNum->SetFocus();
    }
    
    BEGIN_MESSAGE_MAP(CAdditionDialog, CDialog)
       ON_COMMAND(IDC_ADD, OnAdd)
       ON_COMMAND(IDC_CLEAR, OnClear)
    END_MESSAGE_MAP()
    
    class CAdditionApp : public CWinApp
    {
    public:
    	BOOL InitInstance()
    	{
    		CAdditionDialog addition_dialog;
    
    		addition_dialog.DoModal();
    		return FALSE;
    	}
    } additionApp;
    Although the program is running after I attempt the solution above, but the calculation is not running properly. It keeps come out with error message everytime I do the calculation. I have check the documentation but I cannot find any information that say how to do the proper cast from char to char *. Can you guys help me on this problem? Thank you for your help.

  2. #2
    CSharpener vart's Avatar
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    char szText(TEXT_SIZE + 1);

    should be

    char szText[TEXT_SIZE + 1];
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  3. #3
    C++まいる!Cをこわせ! Elysia's Avatar
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    Posts
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    MFC6 is very old, but GetWindowText has an overload for taking a CString instead of char*, so you should use that one if it exists (if it exists for MFC6, which I don't know).
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  4. #4
    Cat without Hat CornedBee's Avatar
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    8,893
    It does. But it was called MFC 4 back then.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

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