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Calling c++ function from qml

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  • L Offline
    L Offline
    lgeyer
    wrote on last edited by
    #12

    Yes, you will have to <code>#include "main.moc"</code> as well.

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    • R Offline
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      rockstar
      wrote on last edited by
      #13

      Lukas, when i include it, it is saying that

      main.moc:no such file or directory

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      • L Offline
        L Offline
        lgeyer
        wrote on last edited by
        #14

        What kind of toolset are you using? qmake should add a call to <code>moc</code> automatically. You might take a look at your compile output if <code>moc</code> is acutally called.

        If it is just Qt Creator which complains about the file missing this is absolutely correct. The file is generated at the time you compile your application and thus cannot be found earlier. Just compile your application.

        If you are using Visual Studio you might need to add this step manually (a how to can be found in the forums).

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        • R Offline
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          rockstar
          wrote on last edited by
          #15

          Lukas, can u provide me a small example of how to call c++ functions from qml...this is what i am trying from morning and i am still unsuccessfull........and u asked me about toolset.....actually i am new to qml and qt....so i don't what it is exactly.....

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          • L Offline
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            lgeyer
            wrote on last edited by
            #16

            Are you using Qt Creator? If so, if it is just Qt Creator, which complains about the file missing, just build and run your application. The file you are trying to include is generated on-the-fly when the application is built, and it is absolutely normal that it isn't available at development time.

            !http://img208.imageshack.us/img208/766/filenotfounderror.png! This means you are fine.

            Usually classes in general and classes subclassing QObject in particular are defined in <code>.h</code> files and implemented in <code>.cpp</code>. This way you do not need to mess around with including any generated files.

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            • R Offline
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              rockstar
              wrote on last edited by
              #17

              Lukas, i did as u told me....i included "main.moc"......i cleaned environment......i rebuilt the project and it is still prompting the same error on "build issues" panel ........

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              • L Offline
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                lgeyer
                wrote on last edited by
                #18

                Well, you then either

                • do it the way it is supposed to be done or
                  [quote author="Lukas Geyer" date="1327401808"]Usually classes in general and classes subclassing QObject in particular are defined in <code>.h</code> files and implemented in <code>.cpp</code>. This way you do not need to mess around with including any generated files.[/quote]
                • you pack and upload your current application and link it here, so I can take a look on it.
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                • R Offline
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                  rockstar
                  wrote on last edited by
                  #19

                  http://www.mediafire.com/?b9a9r9t6qq9aoao

                  i uploaded the project.....have a look at it.....thanks in advance......

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                  • L Offline
                    L Offline
                    lgeyer
                    wrote on last edited by
                    #20

                    <code>main.moc</code> is generated as expected and the project compiles fine using MinGW and MSVC2010. Be aware that you have to <code>#include "main.moc"</code> at the end of the source file (or at least after the class definition).

                    I don't know what's the problem on your end.

                    Is there any reason you are not just doing it as it is supposed to be done?

                    [quote author="Lukas Geyer" date="1327401808"]Usually classes in general and classes subclassing QObject in particular are defined in <code>.h</code> files and implemented in <code>.cpp</code>. This way you do not need to mess around with including any generated files.[/quote]

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                    • R Offline
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                      rockstar
                      wrote on last edited by
                      #21

                      i am using qt creator......

                      actually till yesterday i was doing programs only using qml.....this is my first project using both cpp and qml ......

                      i thought it was easy but it's not.......

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                      • L Offline
                        L Offline
                        lgeyer
                        wrote on last edited by
                        #22

                        It actually is easy.

                        Please don't get me wrong - but I have told you for the third time now how it is supposed to be done and how to circumvent the need of including generated files and I still sense that you do not even properly read what I write.
                        @
                        // testclass.h

                        class TestClass : public QObject
                        {
                        Q_OBJECT

                        public:
                        TestClass(QObject *parent = 0);

                        Q_INVOKABLE QString returnString();
                        

                        };

                        // testclass.cpp

                        TestClass::TestClass(QObject *parent) : QObject(parent)
                        {
                        }

                        QString TestClass::returnString()
                        {
                        return "string";
                        }

                        // main.cpp

                        int main(int argc, char *argv[])
                        {
                        QApplication application(argc, argv);

                        QDeclarativeView view;
                        
                        view.rootContext()->setContextProperty("TestClass", new TestClass(&view));
                        view.setSource(QUrl::fromLocalFile&#40;"Test.qml"&#41;);
                        view.show();
                        
                        return application.exec&#40;&#41;;
                        

                        }

                        // Test.qml

                        import QtQuick 1.1

                        Text {
                        text: TestClass.returnString()
                        }
                        @

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                        • R Offline
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                          rockstar
                          wrote on last edited by
                          #23

                          thanks a ton Lukas.....it worked....

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                          • M Offline
                            M Offline
                            mathiii
                            wrote on last edited by
                            #24

                            Hey guys,

                            I´m having exactly the same problem, but I think some of the Classes and Libraries have changed. The way Lukas explained this makes a lot of sense to me, but the code doesn´t work for me. I´m using Qt 5.3 with QtQuick 2.2 .
                            I would be very thankful if someone could look at my code, as I´m desperate at the moment.My goal is to write a String into an xml-file.
                            the c++function should be called from qml.

                            Thanks in advance

                            @
                            //header.h
                            class TestClass : public QObject
                            {
                            Q_OBJECT

                            public:
                            TestClass(QObject *parent = 0);

                            Q_INVOKABLE void writeXml(QString &text){ }
                            

                            };@

                            @//func.cpp

                            TestClass::TestClass(QObject *parent) : QObject(parent)
                            {
                            }

                            void TestClass::writeXml(QString text)
                            {

                                    QString filename = "C:/Qt5/Tools/QtCreator/bin/CPPTEST2/example.xml";
                                    QFile file&#40;filename&#41;;
                                    if (file.open(QIODevice::ReadWrite)) {
                                        QTextStream stream(&file);
                                        stream << text << endl;
                                         }
                                    file.close();
                            

                            }@

                            @
                            //main.cpp
                            {
                            QGuiApplication app(argc, argv);

                            QQmlApplicationEngine engine;
                            engine.load(QUrl(QStringLiteral("qrc:///main.qml")));
                            QQuickView *view = new QQuickView;
                            view->setSource(QUrl::fromLocalFile&#40;"qrc:///main.qml"&#41;);
                            view->show();
                            
                            return app.exec();
                            

                            }
                            @
                            @ //main.qml
                            import QtQuick 2.2
                            import QtQuick.Window 2.1

                            Window {
                            visible: true
                            width: 360
                            height: 360

                            MouseArea {
                                anchors.fill: parent
                                onClicked: {
                                    TestClass.writeXml("Hello World");
                                }
                            }
                            

                            }@

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                            • M Offline
                              M Offline
                              messi
                              wrote on last edited by
                              #25

                              Hi mathiii
                              this is not how it works.
                              You have to create a C++ object first.
                              Than make the object for QML visible.
                              Now you can access the object.

                              Check out the following link.
                              It describes every C++/QML interaction:
                              http://qt-project.org/wiki/Introduction_to_Qt_Quick_for_Cpp_developers#e70ea8482b12de725ec779f1bc55c92c

                              Best regards

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