C / C++ / MFC

9-Oct-11 22:31

I have follow code :

C++

// CMyControl.h
	typedef struct ItemData
	{
		LPCTSTR lpszString;
		ItemData();
		ItemData(LPCTSTR lpszStringInit);
		virtual ~ItemData();
	};

// constructor of ItemData struct
CMyControl::ItemData::ItemData(LPCTSTR lpszStringInit)
{
	lpszString = lpszStringInit;
}

I'm not sure if 'lpszString = lpszStringInit' line is correct .... is it ?
Thank you.

john56329-Oct-11 23:37

john5632

9-Oct-11 23:37

I think its correct. Why you are not sure?

_Flaviu9-Oct-11 23:44

9-Oct-11 23:44

Am study a little bit the problem and I found that LPCSTR is const char* and I try it to modify with lpszString = lpszStringInit ... I'm wrong ?

_Flaviu9-Oct-11 23:47

9-Oct-11 23:47

I try also to modify LPCTSTR lpszString; data member to LPSTR lpszString; but I don't know how to copy an LPCTSTR to LPSTR ...

Chandrasekharan P10-Oct-11 0:12

Chandrasekharan P

10-Oct-11 0:12

Is your code compiling?? and put a debug point at

Flaviu2 wrote:
lpszString = lpszStringInit;

and see if the value is getting pased

Every new day is another chance to change your life.

_Flaviu10-Oct-11 0:17

10-Oct-11 0:17

In most of cases, but I meet a situation that in lpszString I have bugs ...

_AnsHUMAN_ 10-Oct-11 1:36

_AnsHUMAN_

10-Oct-11 1:36

Read The Complete Guide to C++ Strings, Part II - String Wrapper Classes[^] series

You talk about Being HUMAN. I have it in my name
AnsHUMAN

Re: may i also add

App_10-Oct-11 7:12

App_

10-Oct-11 7:12

more here

Re: may i also add

_Flaviu10-Oct-11 20:43

10-Oct-11 20:43

Thank you.

Stefan_Lang10-Oct-11 1:42

Stefan_Lang

10-Oct-11 1:42

Syntactically it's correct. Semantically however... only you can say if it is.

What you are doing there is take a pointer to a string and copy it to another pointer. Now both pointers point to the same string. This may be ok, but what if the argument passed to this function was a temporary object and is deleted later? In that case the pointer lpszString in your class will be invalid! Or, even worse, if the string later gets changed somewhere, this will effect your ItemData struct as well! Do you want that?

Advice: Unless you are totally certain no one else but you will ever use this struct ItemData and potentially use it in the way described above, you should take precautions against that: instead of just copying the pointers, you should copy the entire string! Of course, if you do that you should also delete that string in your destructor. It should be roughly like this (didn't actually try it out):

C++

// constructor of ItemData struct
CMyControl::ItemData::ItemData(LPCTSTR lpszStringInit)
{
   if (lpszStringInit != 0  {
      std::size_t length = _tcslen(lpszStringInit);
      lpszString = new TCHAR[length+1];
      _tcscpy(lpszString, lpszStringInit);
   }
   else {
      lpszString = 0;
   }
}
// destructor
CMyControl::ItemData::~ItemData() {
   delete [] lpszString;
}

Now you're sure your ItemData object contains it's own copy that cannot be changed or deleted from the outside, no matter who uses this struct. And you know this copy will be deleted exactly when the ItemData object gets deleted. so there will be no memory leaks caused by your struct.

_Flaviu10-Oct-11 2:30

10-Oct-11 2:30

Thank you all. But what it would be if I use an CString variable instead of LPSTR lpszString ? It would more easy ?

Button Creation, Handling the Click event

Stefan_Lang10-Oct-11 2:33

Stefan_Lang

10-Oct-11 2:33

Yes, if your internal variable is of type CString, then, assigning another CString value to it (or even a LPCTSTR) will automatically do the copying of the string for you, and you don't need to take extra care for releasing it either. That is what string classes are good for.

jkirkerx9-Oct-11 9:29

9-Oct-11 9:29

I searched for hours, but everything was C# or C++ mfc.

I created a button, using CreateWindow, I found it on a tutorial site on how to make window controls, but there no example on how to handle the click.

So I wrote this, am I missing something like a SendMessage to register the button?

HWND bt_IIS_Install;
		bt_IIS_Exit = CreateWindow(L"button", L"Exit", WS_CHILD,
			winWidth / 2 - 200,
			winHeight - 90,
			180, 32, h_IIS_Install_Client, NULL, GetModuleHandle(NULL), 0
		);
		ShowWindow( bt_IIS_Exit, SW_SHOW);

I found this, that handles a dialog response, so I'm guessing that this is how I capture the button clicks, but I need to assign the defintion to the button.

case WM_COMMAND:
            if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
            {
                //EndDialog(hDlg, LOWORD(wParam));
                //return (INT_PTR)TRUE;
            }

            break;

Am I on the right track here?

Niklas L9-Oct-11 9:43

Niklas L

9-Oct-11 9:43

You should use the hMenu parameter to specify the control id of your button (IDOK or IDCANCEL in your case)

From MSDN:
hMenu [in, optional]
A handle to a menu, or specifies a child-window identifier depending on the window style. For an overlapped or pop-up window, hMenu identifies the menu to be used with the window; it can be NULL if the class menu is to be used. For a child window, hMenu specifies the child-window identifier, an integer value used by a dialog box control to notify its parent about events. The application determines the child-window identifier; it must be unique for all child windows with the same parent window.

jkirkerx9-Oct-11 10:30

9-Oct-11 10:30

Thanks for the quick response, who works on Sunday.

I understand, I just need to turn the gears awhile to produce something that works.

jkirkerx9-Oct-11 13:19

9-Oct-11 13:19

Well that took awhile to figure out. I created a menu in my resource file, and assigned the number to it in the other resource file. Then added the single hMenu item to the create window so WM_COMMAND can pick it up as the wParam. Thanks for the pointer to the huge lesson that I really learned from.

HWND bt_IIS_Install;
		bt_IIS_Exit = CreateWindow(L"BUTTON", L"Exit", WS_CHILD,
			winWidth / 2 - 200,
			winHeight - 90,
			180, 32, hIIS_Install, (HMENU)IDC_IIS_WS_EXIT, GetModuleHandle(NULL), 0
		);
		ShowWindow( bt_IIS_Exit, SW_SHOW);

«_Superman_»9-Oct-11 16:47

«_Superman_»

9-Oct-11 16:47

I did this in one of my articles - Mousey! Roll Over and Park[^]
The settings dialog and all its controls are created using CreateWindow.

«_Superman_»
I love work. It gives me something to do between weekends.

Microsoft MVP (Visual C++)

Polymorphism in C

jkirkerx9-Oct-11 17:44