Multiple inheritance

Hallo !

I have some views which handle partly the same commands (e.g. every view has a "OnEditCopy") in the same way.

Thus I want to share that code in a common base class, but my views derive from different base-classes (CRichEditView, CEditView, CTextView...).

Normally it's impossible with MFC to have two base-classes which both derive from CWnd

=> Does anybody know a solution for this ??

Thanks,
CORCOR

Multiple inheritance is always :(

Why not using a class "between" CView and your classes?

CView
|
|
CMyViewBase (with the OnEditCopy-Command-Handlers)
|
|
CMySpezialView1 (with the spezial Command-Handlers or with OnEditCopy, if this class handles this event on another way then CMyViewBase)


Another idea would be using macros.

I can't use a class "between", because not all my views derive from CView.
E.g. one derives from CRichEditView (which derives from CView)

So where would be "between" ?

Since you are saying that the code is essential the same,
Why dont you simply put it inside the document class or
some other class and make the function a friend to the
view class ?

when ever you need to exec the common code(fn) you could
pass a pointer the view on which to act and voila
your problem is sovled !


CDocument::CommonCode(View*pView) ;


class View1 : ..
{

friend CDocument::CCommonCode(pView* pView) ;
..
..
};


..
..

Yeah, I also can put it in a "not - CWnd derived class" and derive my views from this class and the old base class, like

class CMyViewBase
{
void DoEditCopy();
}

class CMySpezialView1 : public CScrollView, public CMyViewBase
{
afx_msg void OnEditCopy();
}

void CMySpezialView1::OnEditCopy()
{
DoEditCopy();
}

but then, I need for EACH view and EACH command
*) ON_COMMAND(...)
*) ON_UPDATE_COMMAND_UI(...)
*) OnEditCopy
*) OnUpdateEditCopy
:(

Every time I add a new command, I have to go through all views to attach the command / update-command handlers and maybe forget on view....

So my goal is to modify one class and automatically have it in all views.

may templates help ?

Why don't u use CFormView where u can place richedit control and edit control and static text control?

U can control which control is visible and enabled, and and 'stretch' the whatever richedit control to fill the whole client area.

FYI CFormView is like a dialog where u can place controls in it.

Quote:

---

Originally posted by corcor
Yeah, I also can put it in a "not - CWnd derived class" and derive my views from this class and the old base class, like

class CMyViewBase
{
void DoEditCopy();
}

class CMySpezialView1 : public CScrollView, public CMyViewBase
{
afx_msg void OnEditCopy();
}

void CMySpezialView1::OnEditCopy()
{
DoEditCopy();
}

but then, I need for EACH view and EACH command
*) ON_COMMAND(...)
*) ON_UPDATE_COMMAND_UI(...)
*) OnEditCopy
*) OnUpdateEditCopy
:(

Every time I add a new command, I have to go through all views to attach the command / update-command handlers and maybe forget on view....

So my goal is to modify one class and automatically have it in all views.

---

If the implementation for each method will be the same or very close, why not use a shim class to avoid all the rewriting?

template <deriv,base>
class shim : public base
{
protected:
virtual ON_COMMAND(...)
virtual ON_UPDATE_COMMAND_UI(...)
virtual OnEditCopy
virtual OnUpdateEditCopy
}

then you could declare each view like this:

class CNewView : public shim <CNewView,cMyViewBase>
{
//any extra methods can go here
};

class CAnotherNewView : public shim <CAnotherNewView,cMyRichEditViewBase>
{
//any extra methods can go here
};

In doing that most all implementation details can be held in the shim, and you can override where you need something different.