How to extend a class ?

Hello !

It's my first post so please be patient :D.

I work on Code::Blocks and Qt 4.1.

I wonder how it is possible to extend, for exemple, a QListView ?

Here is what I tried without positive result :

QListViewExt.h :

Code:

---

// promoted widget QListView -> QListViewExt
#ifndef QLISTVIEWEXT_H
#define QLISTVIEWEXT_H
 
#include <qlistview.h>
 
 
class QListViewExt : public QListView
{
    Q_OBJECT
public:
    QListViewExt(QWidget *parent = 0, const char *name = 0);
    ~QListViewExt();
};
 
#endif

---

and the associated moc file where the problem is :

Code:

---

/****************************************************************************
** Meta object code from reading C++ file 'qlistviewext.h'
**
** Created: dim. 25. juin 10:56:43 2006
**      by: The Qt Meta Object Compiler version 59 (Qt 4.1.3)
**
** WARNING! All changes made in this file will be lost!
*****************************************************************************/
 
#include "qlistviewext.h"
#if !defined(Q_MOC_OUTPUT_REVISION)
#error "The header file 'qlistviewext.h' doesn't include <QObject>."
#elif Q_MOC_OUTPUT_REVISION != 59
#error "This file was generated using the moc from 4.1.3. It"
#error "cannot be used with the include files from this version of Qt."
#error "(The moc has changed too much.)"
#endif
 
// The problem is at this line
// The problem is at this line
static const uint qt_meta_data_QListViewExt[] = {
// error : 'uint' does not name a type
// error : 'uint' does not name a type
 
 // content:
       1,       // revision
       0,       // classname
       0,    0, // classinfo
       0,    0, // methods
       0,    0, // properties
       0,    0, // enums/sets
 
       0        // eod
};
 
static const char qt_meta_stringdata_QListViewExt[] = {
    "QListViewExt\0"
};
 
const QMetaObject QListViewExt::staticMetaObject = {
    { &QListView::staticMetaObject, qt_meta_stringdata_QListViewExt,
// The problem is at this line
// The problem is at this line
      qt_meta_data_QListViewExt, 0 }
// error :  : 'qt_meta_data_QListViewExt' was not declared in this scope
// error :  : 'qt_meta_data_QListViewExt' was not declared in this scope
};
 
const QMetaObject *QListViewExt::metaObject() const
{
    return &staticMetaObject;
}
 
void *QListViewExt::qt_metacast(const char *_clname)
{
    if (!_clname) return 0;
    if (!strcmp(_clname, qt_meta_stringdata_QListViewExt))
	return static_cast<void*>(const_cast<QListViewExt*>(this));
    return QListView::qt_metacast(_clname);
}
 
int QListViewExt::qt_metacall(QMetaObject::Call _c, int _id, void **_a)
{
    _id = QListView::qt_metacall(_c, _id, _a);
    if (_id < 0)
        return _id;
    return _id;
}

---

(so there are two erros (in red comments))

If you need more information... just ask ;) !

Thanks !

edit:
1) added semi-colon at and of class definition

I think the problem is because you forgot the semi-colon at the end of your class declaration.

Thanks for that notification but that doesn't solve the problem. In fact, I think the compiler would show it if it was gone to that line !

Conclusion... that is a little more difficult !

Quote:

---

Originally Posted by agent007se

Conclusion... that is a little more difficult !

---

How do you build your application? Do you use qmake?

Quote:

---

Originally Posted by jacek

How do you build your application? Do you use qmake?

---

I use a little tool called qt-prebuild which is fully functionnal because I already compiled other Qt based programs very well without difficulties so it must call qmake nicely to do that.

edit: of course that program run uic.exe, moc.exe and so on... all what's needed to compile.

Quote:

---

Originally Posted by agent007se

I already compiled other Qt based programs very well without difficulties so it must call qmake nicely to do that.

---

Are you sure that there are no other errors? Maybe your compiler can't find Qt headers?

Try putting this on line 18 of MOC'ed file.

Code:

---

typedef unsigned int uint

---

Then we might get other errors due to some Qt include related configuration.

Quote:

---

Originally Posted by bits

Try putting this on line 18 of MOC'ed file.

Code:

---

typedef unsigned int uint

---

Then we might get other errors due to some Qt include related configuration.

---

That wasn't the problem !

I solved the problem with deleting all "crap" files that weren't needed anymore and now it works BUT I have a new problem which fit nicely with the title of this topic so we can continue now :

here is the output :

Quote:

---

Linking executable: C:\test\app.exe
.objs\moc_qlistviewext.o:moc_qlistviewext.cpp:(.rd ata$_ZTV12QListViewExt[vtable for QListViewExt]+0x14): undefined reference to `QListViewExt::~QListViewExt()'
.objs\moc_qlistviewext.o:moc_qlistviewext.cpp:(.rd ata$_ZTV12QListViewExt[vtable for QListViewExt]+0x18): undefined reference to `QListViewExt::~QListViewExt()'
.objs\moc_qlistviewext.o:moc_qlistviewext.cpp:(.rd ata$_ZTV12QListViewExt[vtable for QListViewExt]+0x190): undefined reference to `non-virtual thunk to QListViewExt::~QListViewExt()'
.objs\moc_qlistviewext.o:moc_qlistviewext.cpp:(.rd ata$_ZTV12QListViewExt[vtable for QListViewExt]+0x194): undefined reference to `non-virtual thunk to QListViewExt::~QListViewExt()'
collect2: ld returned 1 exit status
Process terminated with status 1 (0 minutes, 10 seconds)
0 errors, 0 warnings

---

I think that the better thing to do is restarting a new and clean project file because I'll use a QTreeWidget which have the function I wanted so that I don't need to extend anything !

Thanks for trying to help me !

Oh, last thing, can you say me if there is a "default" structure of tree in QTreeView like in QTreeWidget ?

Quote:

---

Originally Posted by agent007se

undefined reference to `QListViewExt::~QListViewExt()'

---

Maybe you forgot to implement the destructor?

Quote:

---

Originally Posted by jacek

Maybe you forgot to implement the destructor?

---

Please, can you give me a minimal implementation of qlistviewext.cpp in regard of the qlistviewext.h ?

I have some difficulties to do that because I'm just beginning with "serious" things with Qt !!

I'll give you a thank just after that :D !!

Quote:

---

Originally Posted by agent007se

Please, can you give me a minimal implementation of qlistviewext.cpp in regard of the qlistviewext.h ?

---

Code:

---

QListViewExt::QListViewExt( QWidget *parent, const char *name )
   : QListView( parent )
{
   setObjectName( name );
}
 
QListViewExt::~QListViewExt()
{
   // empty
}

---

Your constructor signature looks like if you were trying to use Qt3, not Qt4. Qt4 doesn't use name parameter in widget constructors.

Well, it work like a charm now :D.

- Removed the name because I was using an old howto !
- Added the desctructor

Thanks again ;) !