Question on QPointer(solved)

houmingc

#include <QLabel>
#include <QApplication>
error: QWidget: Must construct a QApplication before a QWidget

QPushButton* button11 = new QPushButton("PEC 1");
int main(int argc, char ** argv)
{
QApplication app(argc, argv);
button11->text("Hello");
return app.exec();
}

Will the below code resolve the error?
---------------------------- My remedy-----------------------
QPointer<QPushButton> button11 = new QPushButton("PEC 1");
int main(int argc, char ** argv)
{
QApplication app(argc, argv);
button11->text("Hello");
return app.exec();
}

KiwiJeff

No, the problem is that you create a QWidget before your QApplication is constructed. Try the following:

QPointer<QPushButton> button11;
int main(int argc, char ** argv)
{
    QApplication app(argc, argv);
    button11 = new QPushButton("PEC 1");
    button11->text("Hello");
    return app.exec();
}

houmingc

Because i am coding in main, i created myslots.h to QObject::connect
Is it possible to tell compiler that the variable declaration is already declared in main.cpp

----------------myslots.h---------------------------
extern QPointer<QPushButton> button11;

KiwiJeff

I think the thread topic is no longer relevant to your problem and thus maybe you should start a new thread.

Either way, I am not sure what your goal or use case is that you need to work in main and declare connects in a header and thus use an extern declaration.