[Dev-C++] wxwindows: Problem with inheritance

[Glen V. <gve...@pa...>]

First of all: I'm quite a newbie at OO programming in C++ ;)
Now for the problem:
1. Since yesterday I'm following the wxTutorial.pdf (from the wxwindows 
site) and am trying out the stuff I read there.
I copied the example on how to only let numeric chars get through to the 
textctrl (deriving wxTextCtrl to NumTextCtrl) and it worked.
Later on I saw the example on using the function "bool 
wxTextCtrl::IsModified()" (for learning to "use wxCloseEvent::Veto()").
It works when using the class wxTextCtrl, but not with class NumTextCtrl 
where it alway returns a false. I thought that functions supported by 
the parent automatically are available to the child (using 
NumTextCtrl::OnChar()  at least verifies this, so the problem prolly is 
somewhere else)?
Overriding the function to NumTextCtrl::IsModified(){ return true; } works.

2. I also had a problem including NumTextCtrl.h. It needed to be 
included in TextFrame.h and not in TextFrame.cpp (where all the other 
wx-stuff is included)
Is there a logic behind this or did I somehow broke something?
=================================================================
NumTextCtrl.h:

#ifndef _NUMTEXTCTRL_H
#define _NUMTEXTCTRL_H
    class NumTextCtrl: public wxTextCtrl{
        public:
        //variables:
       
        //Functions:
            NumTextCtrl(wxWindow *parent);
            void OnChar(wxKeyEvent &event);
            //bool IsModified();
       
        protected:
            DECLARE_EVENT_TABLE()
    };
#endif

================================================================
NumTextCtrl.cpp:

#include "wx/wxprec.h" 

#ifndef WX_PRECOMP
    #include "wx/wx.h"
#endif

#include "NumTextCtrl.h"   

NumTextCtrl::NumTextCtrl(wxWindow *parent): wxTextCtrl(parent,-1){}

void NumTextCtrl::OnChar(wxKeyEvent &event){
    if (isdigit(event.GetKeyCode())){
        event.Skip();
    }
    else{
        wxBell();
    }
}

/*
bool IsModified(){
    return true;   //This works
}
*/

BEGIN_EVENT_TABLE(NumTextCtrl, wxTextCtrl)
    EVT_CHAR(NumTextCtrl::OnChar)
END_EVENT_TABLE()
=========================================================================
TextFrame.h (main frame of the app)

#include "NumTextCtrl.h"
#ifndef _TEXTFRAME_H
#define _TEXTRAME_H
    class TextFrame: public wxFrame{
        public:
            //constructor
            TextFrame(const wxChar *title, int xpos, int ypos, int 
width, int height);
           
            //Destructor
            ~TextFrame();
           
            void OnMenuFileOpen(wxCommandEvent &event);
            void OnMenuFileSave(wxCommandEvent &event);
            void OnMenuFileQuit(wxCloseEvent &event);
            void OnMenuInfoAbout(wxCommandEvent &event);
           
        protected:
            DECLARE_EVENT_TABLE()
       
        private:
            NumTextCtrl *m_pNumTextCtrl; 
            wxMenuBar *m_pMenuBar;
            wxMenu *m_pFileMenu;
            wxMenu *m_pInfoMenu;
           
            enum{                    
                MENU_FILE_OPEN,
                MENU_FILE_SAVE,
                MENU_FILE_QUIT,
                MENU_INFO_ABOUT
            };
    };
#endif
===========================================================================
TextFrame.cpp:

#include "wx/wxprec.h" 
#ifndef WX_PRECOMP
    #include "wx/wx.h"
#endif
#include "TextFrame.h"

TextFrame::TextFrame(const wxChar *title, int xpos, int ypos, int width, 
int height)
        : wxFrame((wxFrame *) NULL, -1, title, wxPoint(xpos, ypos), 
wxSize(width, height)){       
        //Constructor immediately redirects parameters to parents' 
constructor
    
    m_pNumTextCtrl = new NumTextCtrl(this);
                               
    m_pMenuBar = new wxMenuBar();   
   
    m_pFileMenu = new wxMenu();
    m_pFileMenu->Append(MENU_FILE_OPEN, "&Open", "Opent een file");
    m_pFileMenu->Append(MENU_FILE_SAVE, "&Save", "Bewaart huidige file");
    m_pFileMenu->Append(wxID_CLOSE, "&Quit", "Geefetop");
    m_pMenuBar->Append(m_pFileMenu, "&File");
   
    m_pInfoMenu = new wxMenu();
    m_pInfoMenu->Append(MENU_INFO_ABOUT, "&Help", "Toont help-menu");
            m_pMenuBar->Append(m_pInfoMenu, "&About");
   
    this->SetMenuBar(m_pMenuBar);   //"this->" is optional, but as a 
newb I prefer   
    this->CreateStatusBar(3);       //clear distinction between methods 
and functions
    this->SetStatusText("Wippieeee", 1);
}

TextFrame::~TextFrame(){}

BEGIN_EVENT_TABLE(TextFrame, wxFrame)
    EVT_MENU(MENU_FILE_OPEN, TextFrame::OnMenuFileOpen)
    EVT_MENU(MENU_FILE_SAVE, TextFrame::OnMenuFileSave)
    EVT_MENU(wxID_CLOSE, TextFrame::OnMenuFileQuit)
    EVT_MENU(MENU_INFO_ABOUT, TextFrame::OnMenuInfoAbout)
END_EVENT_TABLE()

void TextFrame::OnMenuFileOpen(wxCommandEvent &event){
    wxLogMessage("File Open Menu Selected");
}

void TextFrame::OnMenuFileSave(wxCommandEvent &event){
    wxLogMessage("File Save Menu Selected");
}

void TextFrame::OnMenuFileQuit(wxCloseEvent &event){
    bool destroy = true;
    if(event.CanVeto()){                     
        if(m_pNumTextCtrl->IsModified()){
            wxMessageDialog *dlg = new wxMessageDialog(this,
                                    "Text is changed!\nAre you sure to 
exit?",
                                    "Text Changed!!!", wxYES_NO | 
wxNO_DEFAULT);
            int result = dlg->ShowModal();
            if (result == wxID_NO){
                event.Veto();
                destroy = false;
            }
        }
    }
    if(destroy){
        Destroy();
    }
}

void TextFrame::OnMenuInfoAbout(wxCommandEvent &event){
    wxLogMessage("Help About Menu Selected");
}