Include problems

[Nevyn]

Hi, i've got a problem with the following declarations

file list.h
-----------
class listOfItem : public QPtrList<Item>
{

[Victor Bazarov]

Re: Include problems

"Nevyn" <nevynZEROSPAM@ hotmail.com> wrote...[color=blue]
> Hi, i've got a problem with the following declarations
>
> file list.h
> -----------
> class listOfItem : public QPtrList<Item>
> {
> .
> .
> .
> }
>
> ----
>
> file multiple.h
> --------------------
> class Item
> {
> private:
> listOfItem: list1, list2;
> .
> .
> .
> }
>
> how should i include the above files?[/color]

For starters, you should learn to always post real code by copy-
and-paste operation instead of typing it into the message.
[color=blue]
> whatever i tried resulted in errors[/color]

Perhaps you should change the 'Item' to contain a pointers to lists:

class listOfItem;

class Item
{
listOfItem *list1, *list2;
...
};

That allows you to only forward-declare the class instead of having
to include the definition.

Victor

[Nevyn]

Re: Include problems

On Mon, 11 Aug 2003 10:03:22 -0400, Victor Bazarov wrote:

[color=blue]
> Perhaps you should change the 'Item' to contain a pointers to lists:
>
> class listOfItem;
>
> class Item
> {
> listOfItem *list1, *list2;
> ...
> };
>
> That allows you to only forward-declare the class instead of having to
> include the definition.
>[/color]
Thanks for your answer Victor but given that i must use list1 & list2 in
some method of Item (e.g. count total elements in lists) i have to call
the 'new' statement for those listOfItem in the Item constructor... thus i
always end with the same problems... or am i missing something?

thanks a lot

[Victor Bazarov]

Re: Include problems

"Nevyn" <nevynZEROSPAM@ hotmail.com> wrote...[color=blue]
> On Mon, 11 Aug 2003 10:03:22 -0400, Victor Bazarov wrote:
>
>[color=green]
> > Perhaps you should change the 'Item' to contain a pointers to lists:
> >
> > class listOfItem;
> >
> > class Item
> > {
> > listOfItem *list1, *list2;
> > ...
> > };
> >
> > That allows you to only forward-declare the class instead of having to
> > include the definition.
> >[/color]
> Thanks for your answer Victor but given that i must use list1 & list2 in
> some method of Item (e.g. count total elements in lists) i have to call
> the 'new' statement for those listOfItem in the Item constructor... thus i
> always end with the same problems... or am i missing something?[/color]

Yes, you're missing that you're allowed to put the Item's constructor
into a separate file and not the 'Item' class definition. The order of
compilation for Item's constructor would be

Forward-declare class listOfItem.
Define class Item.
Define class listOfItem.
Define Item::Item.

Victor

[Nevyn]

Re: Include problems

On Mon, 11 Aug 2003 11:50:52 -0400, Victor Bazarov wrote:

[color=blue]
> Yes, you're missing that you're allowed to put the Item's constructor
> into a separate file and not the 'Item' class definition. The order of
> compilation for Item's constructor would be
>
> Forward-declare class listOfItem.
> Define class Item.
> Define class listOfItem.
> Define Item::Item.
>[/color]
Nope, that was not what i was missing :-) i was trying instead to define
class ListOfItem (capital L)

after having pre-declared
class listOfItem (no capital) !!!

silly of me :-(

Now i am wondering (just out of curiosity) is there a way to solve the
above problem without using pointers?

thanks a lot

[Victor Bazarov]

Re: Include problems

"Nevyn" <nevynZEROSPAM@ hotmail.com> wrote...[color=blue]
> [...]
> Now i am wondering (just out of curiosity) is there a way to solve the
> above problem without using pointers?[/color]

Try using references... :-)

Actually this compiles:
---------------------------------------------------- listOfT.h
template<class T> class listOfT {
T* head;
public:
listOfT() : head(0) {}
};
---------------------------------------------------- Item.h
#include <listOfT.h>
class Item;
typedef listOfT<Item> listOfItem;

class Item {
listOfItem list;
};
---------------------------------------------------- main.cpp
#include <Item.h>
int main() {
Item it;
}
---------------------------------------------------------------

HTH

Victor

[Agent Mulder]

Re: Include problems

Neyvn> how should i include the above files?
Neyvn> whatever i tried resulted in errors

#include <vector>
class Item;
class listOfItem:publ ic std::vector<Ite m>{};
class Item {private:listOf Item list1,list2;};
int main(int argc,char**argv )
{
listOfItem listofitem;
Item item;
return 0;
}

-X