C / C++ / MFC

BOOL COptionsDlg::OnInitDialog()
{
	CDialog::OnInitDialog();
	SetCapture();//Thank you Iain
	return TRUE;
}

void COptionsDlg::OnNcDestroy()
{//Thanks to DavidCrow
	CDialog::OnNcDestroy();
	delete this;
}

void COptionsDlg::OnLButtonUp(UINT nFlags, CPoint point)
{//Thanks to Iain
	CDialog::OnLButtonUp(nFlags,point);
	CRect rect;
	this->GetWindowRect(rect);
	DWORD pos=GetMessagePos();
	point=CPoint(LOWORD(pos),HIWORD(pos));
	if(!rect.PtInRect(point)){this->DestroyWindow();}//close only if click was outside of the window
}

//I think you know graphing calculators...
class WindowOptions {
public:
	double xmin;
	double xmax;
	double xscl;
	double ymin;
	double ymax;
	double yscl;
};

struct Options
{
   double xmin;
   ...
};

class CMyApp
{
...
   Options m_Options;
...
};

In your main frame, you have a menu handler:
void CMainFrame::OnToolsOptions ()
{
   CMyOptionsDlg *pDlg = new CMyOptionsDlg; // make a new options dlg - it will self delete.
   CMyApp *pApp = (CMyApp *) AfxGetApp ();
   dlg->m_pOptions = &(pApp->m_Options); // give the dialog a pointer to the options struct.

   dlg->Create (this);  // make the dialog window
}

void COptionDlg::DoDataExchange (CDataExchange *pDX)
{
   ASSERT(m_pOtions);
   if (!m_pOptions) return;

   // get/set a double from an edit box
   DDX_Text (pDX, IDC_XMIN, m_pOptions->xmin);
   ...
}

// Create only 3 objects in class demo.

#include <iostream.h>

static int nCount = 0;

class Demo
{
public:
    Demo()
    {
        nCount++;
    }
};

bool IsMax()
{
    if(nCount>3)
        return true;
    else
        return false;
}
    
int main()
{
    // here is 4 objects.
    Demo d1,d2,d3,d4;
    if(IsMax())
    {
        cout<<"error"<<endl;
    }
    return 0;
}

Rajesh R Subramanian wrote:

If you don't stop using multiple logins

p_1960 wrote:

if i want to create only 3 objects how can i restrict the class to do the same...

p_1960 wrote:

...how can i restrict the class to do the same...

es1968 wrote:

May I get an accurate explantion why this is the display for each stage ?

es1968 wrote:

why after stage 6, str1 and strref have not been changed after str2 changed to "bb" ?

#include <string>
using namespace std;
#include <stdio.h> 
void main()
{
	// case 0
	string str1 = "a";
	string str2 = "b";
	string * const pstr = &str1;//that's wath a reference really is

	printf("\ncase 0\n str1: %s", str1.c_str());
	printf("\n str2: %s", str2.c_str());
	printf("\n refstr: %s\n ", (*pstr).c_str());
	
	// case 1
	str1 = "aa";
	
	printf("\n case 1\n str1: %s", str1.c_str());
	printf("\n str2: %s", str2.c_str());
	printf("\n refstr: %s\n ", (*pstr).c_str());

	// case 2
	(*pstr) = str2;

	printf("\n case 2\n str1: %s", str1.c_str());
	printf("\n str2: %s", str2.c_str());
	printf("\n refstr: %s\n ", (*pstr).c_str());

	// case 3
	str2 = "bb";

	printf("\n case 3\n str1: %s", str1.c_str());
	printf("\n str2: %s", str2.c_str());
	printf("\n refstr: %s\n ", (*pstr).c_str());

}