Re: error C2440: 'initializing' : cannot convert from 'class base *' to 'class Derived *' [modified] - C / C++ / MFC Discussion Boards

Re: error C2440: 'initializing' : cannot convert from 'class base *' to 'class Derived *'

C.P.Rajesh17-Apr-08 21:33

C.P.Rajesh

17-Apr-08 21:33

No. Before posting i tried that. It doesn't work. Actuallu what you have written should be modified as
Derived* dd = NULL;
dd = bb;

Re: error C2440: 'initializing' : cannot convert from 'class base *' to 'class Derived *'

Naveen17-Apr-08 21:46

Naveen

17-Apr-08 21:46

C.P.Rajesh wrote:
Actuallu what you have written should be modified as

What I mean is if you want the =operator to, you should code in that way.

C.P.Rajesh wrote:
Derived* dd = NULL;
dd = bb;

This is just an pointer assigment statement. That is bb is assigned to a pointer of Derived not to an object of class Derived. The operator functions you written on the class will work only for object of that class. not for a pointer of it...

nave

[OpenedFileFinder]

Re: error C2440: 'initializing' : cannot convert from 'class base *' to 'class Derived *'

CPallini17-Apr-08 21:48

CPallini

17-Apr-08 21:48

The above code will not work. Poke tongue | ;-P

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

Re: error C2440: 'initializing' : cannot convert from 'class base *' to 'class Derived *'

Naveen17-Apr-08 21:55

Naveen

17-Apr-08 21:55

CPallini wrote:
The above code will not work

And can you tell me why? Since he have overlaoded the operator= (base* aBase), it should definitly work.. I coudnt find any problem... D'Oh! | :doh:

nave

[OpenedFileFinder]

Re: error C2440: 'initializing' : cannot convert from 'class base *' to 'class Derived *'

CPallini17-Apr-08 22:48

CPallini

17-Apr-08 22:48

Naveen wrote:

And can you tell me why?

Of course:
It's class have an assignment operator returning a pointer to Derived not a reference to.
(his design is a bit weird...).
Smile | :)

Re: error C2440: 'initializing' : cannot convert from 'class base *' to 'class Derived *'

Naveen17-Apr-08 22:58

Naveen

17-Apr-08 22:58

Yes yes

I just changed the code so that the operator =() will get called. Forget to change the operator =() function D'Oh! | :doh:

nave

[OpenedFileFinder]

Re: error C2440: 'initializing' : cannot convert from 'class base *' to 'class Derived *'

CPallini17-Apr-08 21:45

CPallini

17-Apr-08 21:45

C.P.Rajesh wrote:
what is wrong in the below code?

Your operator is defined for a hinstance of the object, not for a pointer, the following code will work

base* bb = new Derived;
Derived ddHelper;
Derived* dd = (ddHelper=bb);

Anyway your design is ugly: overloading the assignemnt operator such a way is misleading.
Smile | :)

Re: error C2440: 'initializing' : cannot convert from 'class base *' to 'class Derived *' [modified]

C.P.Rajesh17-Apr-08 21:55

C.P.Rajesh

17-Apr-08 21:55

I didn't understand your reply. My requirement is i need a linked list which stores multiple type of objects in a single list. So i have a data class (a template class) like below

template <class T> class data : public base
{
T myData;

public:
T& getData () {return myData;}
bool putData (const T& aData) {myData = aData; return true;}

// Overloaded operator which takes base class pointer
data<T>* operator= (base* aBase)
{
return (data<T>*)aBase;
}

};

Each node has a base class pointer which stores derived class object. So while retrieving the data from linked list i use this overloaded operator. The advantage is if i use data<wrongdatatype> on left handside of = operation it will give compilation error.

If you have any other suggestion for the problem i will be happy to hear.

modified on Friday, April 18, 2008 4:02 AM

<div class="ForumMod">modified on Friday, April 18, 2008 4:03 AM</div>

Re: error C2440: 'initializing' : cannot convert from 'class base *' to 'class Derived *'

CPallini17-Apr-08 22:55

CPallini

17-Apr-08 22:55

C.P.Rajesh wrote:
If you have any other suggestion for the problem i will be happy to hear.

Two suggestions:
(1) Use standard library containers.
(2) Exploit polymorphism (i.e. on a well designed class hierarchy, ususally you haven't to bother about the real nature of the pointer, taht is Base* or Derived*,instead, you just call methods on it and all will go on fine).
(2.bis) If you really need the exact nature of the pointer, use dynamic_cast.
Smile | :)

Re: error C2440: 'initializing' : cannot convert from 'class base *' to 'class Derived *'

C.P.Rajesh17-Apr-08 23:24

C.P.Rajesh

17-Apr-08 23:24

Thank you very much for your suggestion.
I have a doubt in the first one. Is there any standard library container which stores different data types in one list, i mean first object is 'int', second is some user defined and so on?

In the second suggestion by saying 'Exploit polymorphism' i beleve you are talking about run time polymorphism i.e using virtual functions. But i am afraid i can't do that because the base class doesn't know about the object type to do any manipulation. If i make it a template class then i cannot have a base pointer in node to point to any data type.
Thank you once again for your time and effort.

Re: error C2440: 'initializing' : cannot convert from 'class base *' to 'class Derived *'

jhwurmbach18-Apr-08 2:26

jhwurmbach

18-Apr-08 2:26

C.P.Rajesh wrote:
Is there any standard library container which stores different data types in one list, i mean first object is 'int', second is some user defined and so on?

No. But you could save yourself the complete container hassle, and focus on the conversion.

Or, you could use STL container with boost::any[^]

Boost is quite renowned for their rigid code review and their focus on well thought out concepts.
Its founder list is a who-is-who of the c++-world.

A number of classes from that web site will be part of the next C++ standard library.

Let's think the unthinkable, let's do the undoable, let's prepare to grapple with the ineffable itself, and see if we may not eff it after all.
Douglas Adams, "Dirk Gently's Holistic Detective Agency"

How to Change the Font Dynamically on button control

phanindra varma17-Apr-08 20:39

phanindra varma

17-Apr-08 20:39

hi,

I am developing SDI application ,inherits from FomView.
It is required that i have to use TTF font type(which i downloaded from Ineternet) on button in run time.

Thank u....

Re: How to Change the Font Dynamically on button control

Hamid_RT17-Apr-08 21:00

Hamid_RT

17-Apr-08 21:00

You can use of CFont::Create and use of SetFont.

Re: How to Change the Font Dynamically on button control

softwero18-Apr-08 12:46

softwero

18-Apr-08 12:46

Mira wey, necesitas poner:

CMyView : public CFormView{

CFont fontButton;
//
};

CMyView::OnInitialUpdate(){
LOGFONT lf;
memset(&lf,0,sizeof(lf));
lf.lfHeight=(int)(33);
lf.lfWeight=FW_BOLD;
strcpy(lf.lfFaceName,"Arial");

m_fontButton.CreateFontIndirect(&lf);
GetDlgItem(IDC_MYBUTTON)->SetFont(&fontButton);

}

Re: How to Change the Font Dynamically on button control

phanindra varma18-Apr-08 22:23

phanindra varma

18-Apr-08 22:23

hi..

Thanks for Reply..

But when i try to do the same
but "AkruthiDev1"(ttf font for Hindi)inplace of "Arial"..
the code doesn't work..

In some aticle ,they mention that we have to use EnumFontProc() callback function.

Can u please tell me ,how to use that function.

Re: How to Change the Font Dynamically on button control

softwero22-Apr-08 8:57

softwero

22-Apr-08 8:57

nop. You Need Install the Font, copy the file .ttf to C:windows/Fonts or $system$/Fonts
Open ControlPanel->fontS
go to menu File->Install New Font

Choice your file .ttf for intall in windows

Combo Box issue

Chandrasekharan P17-Apr-08 20:12

Chandrasekharan P

17-Apr-08 20:12

i have a huge folder that has over 200 files.

the format of the file struture os like this

main folder -> 3 sub folders
subfolder1 -> folder1, folder2, folder3 ... foldern
subfolder2 -> folder1, folder2, folder3 ... foldern
subfolder3 -> folder1, folder2, folder3 ... foldern
folder i to n has files

everything together will be some 2 gb of data.

i hope the folder structure is clear

now the requirement is each folder has files and there are headers in each file.
i want to extract the header and show the parameters on the combo box. how do i do that?

Re: Combo Box issue

Hamid_RT17-Apr-08 20:33

Hamid_RT

17-Apr-08 20:33

Im not sure do you need to FindFirstFile/FindNextFile? for show files

Re: Combo Box issue

Iain Clarke, Warrior Programmer17-Apr-08 22:57

Iain Clarke, Warrior Programmer

17-Apr-08 22:57

If your names are very predictable, how about something like:

...
   CString s;
   CFile f;
   for (i = 0; i < 3; i++)
   {
       for (j = 0; ; j++)
       {
           s.Format ("c:\\subfolder%i\\folder%i\\blah.file", i, j);
           if (!f.Open (s, ..., CFile::modeRead, ...))
              break; // run out of sub directories, so escape inner loop.

           f.Read (stuff);
           DoSomething (stuff);
           f.Close ();       
       }
   }

?

Check parameters for yourself - I know CFile::Open has not been done correctly.

If your subfolders have more random names, then you're going to have to use FindFirstFile / FindNextFile. It will be a bit harder, but not lots.

Iain.

Plz sir... ^CPallini ^CPallini abuz drugz, plz plz help urgent.

how can i set the menu position .

vasu_sri17-Apr-08 19:43

vasu_sri

17-Apr-08 19:43

hi ,
In dialog based application i have added one menu bar. this menu working properly before apply the theme. but when i am applying theme to dialog then menu position will be changed and disappeared. y it is happening like this. Confused | :confused:

have any idea to reposition the menu bar?

or any way to solve this problem?

Regards,
Srinivas

SaveDC returning 0

Super Hornet17-Apr-08 19:43

Super Hornet

17-Apr-08 19:43

Actually after 45 hours of endurance test of our application, a crash occured at SaveDC please let me know when the SaveDC fails.

Here the SaveDC is returning 0.

Re: SaveDC returning 0

Hamid_RT17-Apr-08 20:31

Hamid_RT

17-Apr-08 20:31

CAn you more explain?

Re: SaveDC returning 0

Super Hornet17-Apr-08 20:34

Super Hornet

17-Apr-08 20:34

In what cases SaveDc returns 0?

Re: SaveDC returning 0

Hamid_RT17-Apr-08 21:03