MOC and Qt Creator?

[u2gilles]

Hi All,
In the most simple application below, in order to use metaObject I derived QObject and I used Q_OBJECT macro
But Qt Creator does not invoked moc, and as a result the application does not compile .
The test application has 2 files in Qt Creator

main().cpp
@
#include <QtCore/QCoreApplication>
#include <QDebug>
class QObj1 : public QObject {
Q_OBJECT
public:
int i;
};
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QObj1 o1;
qDebug() << o1.metaObject()->className();
qDebug() << o1.objectName();
}

@

qobject2.pro
@
QT += core
QT -= gui
TARGET = qobject2
CONFIG += console
TEMPLATE = app
SOURCES += main.cpp
@

Qt Creator handles moc very well in other applications, but here , moc does not create a moc file and I don’t understand why.
Thanks in advance for your help
Gilles

PS : The compile errors are :
@
23:47:28: Running build steps for project qobject2...
23:47:28: Configuration unchanged, skipping qmake step.
23:47:28: Starting: "C:\dev\Qt\mingw\bin\mingw32-make.exe"
C:/dev/Qt/mingw/bin/mingw32-make.exe -f Makefile.Debug
mingw32-make.exe[1]: Entering directory D:/Source/Cpp/qt5/qobject2-build-desktop-Qt_4_8_1_for_Desktop_-_MinGW__Qt_SDK__Debug' g++ -Wl,-subsystem,console -mthreads -o debug\qobject2.exe debug/main.o -L"c:\dev\Qt\Desktop\Qt\4.8.1\mingw\lib" -lQtCored4 mingw32-make.exe[1]: Leaving directory D:/Source/Cpp/qt5/qobject2-build-desktop-Qt_4_8_1_for_Desktop_-_MinGW__Qt_SDK__Debug'
debug/main.o: In function main': D:\Source\Cpp\qt5\qobject2-build-desktop-Qt_4_8_1_for_Desktop_-_MinGW__Qt_SDK__Debug/../qobject2/main.cpp:15: undefined reference to QObj1::metaObject() const'
debug/main.o: In function QObj1': D:\Source\Cpp\qt5\qobject2-build-desktop-Qt_4_8_1_for_Desktop_-_MinGW__Qt_SDK__Debug/../qobject2/main.cpp:4: undefined reference to vtable for QObj1'
debug/main.o: In function ~QObj1': D:\Source\Cpp\qt5\qobject2-build-desktop-Qt_4_8_1_for_Desktop_-_MinGW__Qt_SDK__Debug/../qobject2/main.cpp:4: undefined reference to vtable for QObj1'
collect2: ld returned 1 exit status
mingw32-make.exe[1]: *** [debug\qobject2.exe] Error 1
mingw32-make.exe: *** [debug] Error 2
23:47:29: The process "C:\dev\Qt\mingw\bin\mingw32-make.exe" exited with code 2.
Error while building project qobject2 (target: Desktop)
When executing build step 'Make'
@

[ChrisW67]

Qmake ensures Moc is run on:

• Files listed in the HEADERS variable. Qmake arranges to compile and link the resulting C++ implementation file by adding it to SOURCES.
• Files listed in the SOURCES or OBJECTIVE_SOURCES variables are processed by moc. Qmake does not link any potential output, so the resulting moc output must be #included.

main.cpp
@
#include <QDebug>
class QObj1 : public QObject {
Q_OBJECT
public:
int i;
};
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QObj1 o1;
qDebug() << o1.metaObject()->className();
qDebug() << o1.objectName();
}
#include "main.moc"
@

As always, if you add or remove Q_OBJECT macros you must rerun qmake.

BTW: Nothing to do with Qt Creator except that it is running qmake on your behalf

[u2gilles]

Thanks Chris. It worked.
I am not 100% it's related to metaObject, but in the corrected code below I can’t display objectName() (which seems to be a dynamic property) and I remember being able to display it in other applications, though not each time. So far, I have never figured out what is missing when it does not display. I hope you can help me to pinpoint it on this simple example.
QObject spec says that "By default, this property contains an empty string" but here i do have metaObject up and running.
qobject2.pro
@
QT += core
QT -= gui
TARGET = qobject2
CONFIG += console
TEMPLATE = app
SOURCES += main.cpp
QObj1.cpp
HEADERS +=
@
QObj1.h
@
#ifndef QOBJ1_H
#define QOBJ1_H
#include <QtCore/QCoreApplication>
class QObj1 : public QObject {
Q_OBJECT
public:
QObj1();
int i;
};
#endif // QOBJ1_H
@

QObj1.cpp
@
#include "QObj1.h"
QObj1::QObj1()
{
}
@

main.cpp
@
#include <QtCore/QCoreApplication>
#include <QDebug>
#include "QObj1.h"
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QObj1 o1;
QObj1 *p1 = new QObj1;
qDebug() << o1.metaObject()->className();
qDebug() << o1.objectName();
qDebug() << p1->objectName();
}
@

output
@
QObj1
“”
“”
@

[sierdzio]

You need to set the objectName property if you want to read it later. This is not done automatically.

[u2gilles]

You are right, it works much better with :
@
o1.setObjectName("op1");
@
I guess it's time for me to do deeper reading on the priority system. Here i mixed up the object name and the instance name.
Thanks again Sierdzio and Chris.