C / C++ / MFC

1-Sep-05 22:25

Hi there, I am using Visual C++ ( 2003 IDE ) and I need to have 2 classes which points to each other. ( The need to be able to call Functions on each other !!!!!
It works fine from mb->ma but when I call mb from ma I get an error : "Use of undefined Typ" or similiar

Can someone help me. Just need to have 2 Classes being able to call funtions on each other...

<br />
////////////////////////////////////////////////////////////////////////////<br />
// Forward Deklaration<br />
class mb;<br />
<br />
class ma<br />
{<br />
    friend class mb;<br />
public:<br />
    ma();<br />
    int ausgabe;<br />
    int mein(void);<br />
    int Callb(void);<br />
    void SetParent(mb *aptrb);<br />
protected:<br />
    mb *_ptrb;<br />
};<br />
int ma::Callb()<br />
{<br />
    int    lreturn = 0;<br />
    mb *lptr = _ptrb;<br />
    //lreturn =  lptr->richtig();            <br />
    //lreturn =  (*lptr).richtig();    <-- Fehler: Hier geht das nicht<br />
    return lreturn;<br />
}<br />
void ma::SetParent(mb *aptrb)<br />
{<br />
    _ptrb = aptrb;<br />
}<br />
ma::ma()<br />
{<br />
    int a = 2;<br />
}<br />
int ma::mein()<br />
{<br />
    return ausgabe;<br />
}<br />
////////////////////////////////////////////////////////////////////////////<br />
class mb<br />
{<br />
public:<br />
    mb();<br />
    ~mb();<br />
    void tuewas(void);<br />
    int richtig(void);<br />
    void SetParent(ma *aptra);<br />
protected:<br />
    ma *ptra;<br />
};<br />
int mb::richtig()<br />
{<br />
    return 500;<br />
}<br />
void mb::SetParent(ma *aptra)<br />
{<br />
    ptra = aptra;<br />
}<br />
mb::mb()<br />
{<br />
    int a = 2;<br />
}<br />
mb::~mb()<br />
{<br />
    int b = 2;<br />
}<br />
void mb::tuewas()<br />
{<br />
    int a = 2;<br />
    // A aufrufen<br />
    ma  *p = ptra;<br />
    if ( p != 0 )<br />
    {<br />
        a = p->mein();<br />
        a = a + 3;<br />
        p->Callb();<br />
       <br />
    }<br />
}<br />
////////////////////////////////////////////////////////////////////////////<br />

Cedric Moonen1-Sep-05 22:30

1-Sep-05 22:30

In the .h files of the mb file, add

class ma;
at the begining of the file.

Then in the .cpp file, include the header of this file.

Fehma1-Sep-05 22:34

1-Sep-05 22:34

I alread did that !!

class B;
class A
{
call something on B --- Wont Work
}

class B
{
Call something on A --- Works
}

Cedric Moonen1-Sep-05 22:50

1-Sep-05 22:50

You mean everything is in one single file ?? All the functions and everything are in the header file ?
It is better to separate the implementations of the class functions in the .cpp file. If you put that in the header file, when you call something from B in the class A, the compiler only knows that the class exists, but it doesn't know what are the members of the class B. So, put all the definitions of the functions (from classA and class B) in a separate .cpp file. And this is much cleaner that having everything in the same file.

Fehma1-Sep-05 23:08

1-Sep-05 23:08

First of all Thank you very mich Cedric for the quick response....

I already had them in seperate .h and .cpp files but the error in Visual studio was the same....
It seems that Visual Studio is having a problem when I call mb from ma ( *p == p->Foo() ) than the Compile is telling me that I don't have a valid type ???

Thanks
Marcus

Cedric Moonen1-Sep-05 23:20

1-Sep-05 23:20

Ok, so if you have forward declaration and all the function defined in a separate .cpp file, this should work (make sure that the header file of class B is included in the .cpp file of class A and the same for class B).

Now, I think this is not due to that fact but probably a syntax error or something like that. It would be really usefull if you post the exact error message (with the error line and everything) and if you could post also the line which gave this error.

Fehma wrote:
*p == p->Foo()

This looks strange to me...

Fehma1-Sep-05 23:55

1-Sep-05 23:55

Thanks I will try it...... Wink | ;-)

With

<*p == p->Foo() > I meant

p->Foo() // Pointer to Object B calls a Function "Foo" on the Object....

Cedric Moonen1-Sep-05 23:59

1-Sep-05 23:59

Fehma wrote:
p->Foo() // Pointer to Object B calls a Function "Foo" on the Object....

Yes, that part I understood but why do you compare the result with the object itself ??
*p

Maybe the problem is there: the compiler cannot convert from the return type (probably an int) to the class B...

Fehma2-Sep-05 0:06

2-Sep-05 0:06

Hey,

sorry that ( *p == ) didn't mean anything !!! he he he
I just had forget to delete it...... Typed to much I guess....

Thousand thanx......

I will try it now with the CPP Files and the correct use of include....

A.ccp will include B.h
and
B.cpp will include A.h

right ??

Fehma2-Sep-05 2:09

Static Control Background Painting

2-Sep-05 2:09

works no !!!! THANK YOU VERY MUCH

Joel Holdsworth1-Sep-05 22:15

Joel Holdsworth

1-Sep-05 22:15

Hi,

I have a question about static controls and how their backgrounds are painted. If I place a static control on a normal dialog, the background of that dialog is a uniform system grey, and the present static seem to paint their own backgrounds to match that. However, in XP property pages, the background is not uniform, it's a kinda whitish gradient fill. How do the static controls erase their backgrounds here? Do they set themselves to be transparent somehow, and let the parent page paint the whole background over which they just draw the text, but not any background, or do they call some function in the parent page asking it to paint a specific portion of background covered by the static control? I'm asking because I need to replicate this effect, in a custom window of mine. Any clues?

Joel Holdsworth

-- modified at 4:19 Friday 2nd September, 2005

Re: Static Control Background Painting

Neagoe Gabriel2-Sep-05 0:04

Neagoe Gabriel

2-Sep-05 0:04

It`s very simple a Static in requesting a brush(OnCtlColor) from it`s parent dialog, to paint it`s background, you have to give a pattern brush with the portion you need... here it`s an example

if( nCtlColor == CTLCOLOR_STATIC )
{
CRect rc;
pWnd->GetWindowRect(&rc);
ScreenToClient(&rc);

CDC *pBDC = new CDC;
CBitmap *pBmp = new CBitmap;
pBDC->CreateCompatibleDC(pDC);
pBmp->CreateCompatibleBitmap(pDC, rc.Width(), rc.Height());
CBitmap *pOLD = (CBitmap*)pBDC->SelectObject(pBmp);

m_pBackgroundBmp->DrawPart( pBDC->GetSafeHdc(),0,0, rc.left, rc.top, rc.Width(), rc.Height());

pBDC->SelectObject( pOLD );

if(m_hbr) DeleteObject(m_hbr);
m_hbr = ::CreatePatternBrush((HBITMAP)pBmp->m_hObject);

pBDC->DeleteDC();
pBmp->DeleteObject();

delete (pBmp);
pBmp = NULL;
delete (pBDC);
pBDC = NULL;

return m_hbr;
}

int h file you have HBRUSH m_hbr;

NG

-- modified at 6:04 Friday 2nd September, 2005

Re: Static Control Background Painting

Joel Holdsworth2-Sep-05 1:15

Joel Holdsworth

2-Sep-05 1:15

Thanks mate. Worked like a charm.

Joel Holdsworth

Difference between Instance and Context

badal_akr1-Sep-05 21:42

badal_akr

1-Sep-05 21:42

Hi guys i sometime get confuse in this?
What is the difference between Instance and Context.
And how two different instances for the same application work.
What are the responsibilities of the OS two maintain the two different instance.
What is the responsibility of the Application developer.
Thanks in advance.

Anil Kumar

Re: Difference between Instance and Context

toxcct1-Sep-05 21:50

toxcct

1-Sep-05 21:50

an instance is a representation in memory of a particuliar type (class, struct, union, native type).

when you write int i1 = 4, i2 = 5;, i1 and i2 are 2 instances of an int.

the context is all that can interract with the program and affect the behavior of it (variables values, thread states...)

TOXCCT >>> GEII power
[toxcct][VisualCalc]

SetForeGroundWindow with XP

dharani1-Sep-05 21:02

dharani

1-Sep-05 21:02

Hi all
I am using VB 6.0 and trying to use SetForeGroundWindow() API in Windows XP . But the API's behavior seems to be different from Non XP OS , because the minimized Application window gets the focus btu waits for a mouse click to come to fore ground . Is there anyway to make the Application window to come to forground straight away ?

regards
Dharani

redindian

khan++1-Sep-05 21:09

khan++

1-Sep-05 21:09

You can use ShowWindow(SW_SHOWNORMAL);

this is this.

ThatsAlok2-Sep-05 0:07

ThatsAlok

2-Sep-05 0:07

dharani wrote:
Is there anyway to make the Application window to come to forground straight away ?

What about [SetWindowPos] api

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV

Marc Soleda2-Sep-05 1:44

Marc Soleda

2-Sep-05 1:44

Are you asking for VB or VC++ code ?

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