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Thread: Need some help with connecting to a signal from coming from QML in c++.

  1. #1
    Join Date
    Mar 2011
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    Qt products
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    Platforms
    Unix/X11 Windows

    Question Need some help with connecting to a signal from coming from QML in c++.

    Hi,

    to learn qt quick and understand better the basics, I made a hello world project in Qt Creator. Now I have thrown out the qmlapplicationviewer class in order to see the most simple functioning qml app and make sure I understand it. Now I get stuck here:

    Qt Code:
    1. // main.cpp
    2.  
    3. #include <QtGui/QApplication>
    4. #include <QDeclarativeView>
    5.  
    6. int main(int argc, char *argv[])
    7. {
    8. QApplication app(argc, argv);
    9.  
    10.  
    11. QDeclarativeView view;
    12. view.setSource(QUrl::fromLocalFile("qml/untitled/main.qml"));
    13.  
    14. // QObject::connect( ( QObject* ) view.engine(), SIGNAL( quit() ),( QObject* ) &app, SLOT( quit() ) );
    15.  
    16. // ^--works | doesn't work --v
    17.  
    18. QObject::connect( view.engine(), SIGNAL( quit() ), &app, SLOT( quit() ) );
    19.  
    20. view.show();
    21.  
    22. return app.exec();
    23. }
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    When i try to build this I get the following error:

    \main.cpp:13: error: no matching function for call to 'QObject::connect(QDeclarativeEngine*, const char*, QApplication*, const char*)'

    qobject.h:198: note: candidates are: static bool QObject::connect(const QObject*, const char*, const QObject*, const char*, Qt::ConnectionType)
    qobject.h:313: note: bool QObject::connect(const QObject*, const char*, const char*, Qt::ConnectionType) const


    Note that the commented out line works as expected... I would think the upcasting should be implicit... In no sample code in the documetation do I see the need for casts...
    Can anyone explain to me what is going on?

    The qml file is unchanged from how the wizard generated it:
    javascript Code:
    1. //main.qml
    2.  
    3. import QtQuick 1.0
    4.  
    5. Rectangle
    6. {
    7. width: 360
    8. height: 360
    9.  
    10. Text
    11. {
    12. text: "Hello World"
    13. anchors.centerIn: parent
    14. }
    15.  
    16. MouseArea
    17. {
    18. anchors.fill: parent
    19. onClicked:
    20. {
    21. Qt.quit();
    22. }
    23. }
    24. }
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    Last edited by wysota; 14th March 2011 at 11:20.

  2. #2
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    Default Re: Need some help with connecting to a signal from coming from QML in c++.

    You're missing:
    Qt Code:
    1. #include <QDeclarativeEngine>
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    Your biological and technological distinctiveness will be added to our own. Resistance is futile.

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