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How to access C++ struct elements in QML

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  • P Offline
    P Offline
    Praveen.Illa
    wrote on 4 Feb 2024, 16:40 last edited by Praveen.Illa 2 Apr 2024, 16:41
    #1

    Hi Team,

    How can I access struct elements declared in Qt-C++ from QML.
    Please find sample piece of code and pls let me know what I am doing wrong
    Thank you

    **Sample.h**
    struct Details : public QObject
     {
              QString deviceName;
     }
    class Sample : public QObject
    {
          Q_PROPERTY(QList<Details *> list READ getList CONSTANT)
    }
    
    **Sample.cpp**
    Sample::Sample()
    {
        Details *dd1 = new Details ;
        dd1->setName("cc1");
        m_list.append(dd1);
    }
    QList<DeviceDetails *> Sample::getList()
    {
        return m_list;
    }
    
    **main.cpp**
    Sample sampleObj;
    engine.rootContext()->setContextProperty("qmlSample", &sampleObj);
    
    **main.qml**
        Column {
            anchors.centerIn: parent
            spacing: 10
            Repeater {
                model: qmlSample.list
    
                delegate: Row {
                    spacing: 10
    
                        Text {
                            text: modelData.deviceName
                            font.pixelSize: 15
                        }
                }
            }
        }
    
    
    S 1 Reply Last reply 5 Feb 2024, 06:30
    0
    • P Praveen.Illa
      4 Feb 2024, 16:40

      Hi Team,

      How can I access struct elements declared in Qt-C++ from QML.
      Please find sample piece of code and pls let me know what I am doing wrong
      Thank you

      **Sample.h**
      struct Details : public QObject
       {
                QString deviceName;
       }
      class Sample : public QObject
      {
            Q_PROPERTY(QList<Details *> list READ getList CONSTANT)
      }
      
      **Sample.cpp**
      Sample::Sample()
      {
          Details *dd1 = new Details ;
          dd1->setName("cc1");
          m_list.append(dd1);
      }
      QList<DeviceDetails *> Sample::getList()
      {
          return m_list;
      }
      
      **main.cpp**
      Sample sampleObj;
      engine.rootContext()->setContextProperty("qmlSample", &sampleObj);
      
      **main.qml**
          Column {
              anchors.centerIn: parent
              spacing: 10
              Repeater {
                  model: qmlSample.list
      
                  delegate: Row {
                      spacing: 10
      
                          Text {
                              text: modelData.deviceName
                              font.pixelSize: 15
                          }
                  }
              }
          }
      
      
      S Offline
      S Offline
      sierdzio
      Moderators
      wrote on 5 Feb 2024, 06:30 last edited by
      #2

      @Praveen-Illa said in How to access C++ struct elements in QML:

      modelData.deviceName

      Just deviceName should be enough.

      I hope you have used Q_OBJECT macro in all these QObject subclasses? And you have initialized parent class properly in constructor?

      Are you getting any error from QML? If not, the problem might be much simpler: your Text, Row, Column elements have no dimensions (width and height).

      (Z(:^

      P 1 Reply Last reply 6 Feb 2024, 05:29
      0
      • S sierdzio
        5 Feb 2024, 06:30

        @Praveen-Illa said in How to access C++ struct elements in QML:

        modelData.deviceName

        Just deviceName should be enough.

        I hope you have used Q_OBJECT macro in all these QObject subclasses? And you have initialized parent class properly in constructor?

        Are you getting any error from QML? If not, the problem might be much simpler: your Text, Row, Column elements have no dimensions (width and height).

        P Offline
        P Offline
        Praveen.Illa
        wrote on 6 Feb 2024, 05:29 last edited by Praveen.Illa 2 Jun 2024, 13:22
        #3

        @sierdzio Hi, Thank you for your response.
        Yes, I have define Q_OBJECT macro in all subclasses.
        Even though, I am not able to access the struct elements.
        Since, the above sample code provided is pseudo code, so I haven't mentioned all the details. sorry for that.
        I came across this below link from stack overflow but I am not sure wether Qt supports or not support exposing struct elements to QML
        https://stackoverflow.com/questions/7980900/qt-qml-c-qlist-of-structs-as-custom-listview-model#:~:text=QML cannot access "low-level,access these properties in QML.

        B 1 Reply Last reply 7 Feb 2024, 13:53
        0
        • P Praveen.Illa
          6 Feb 2024, 05:29

          @sierdzio Hi, Thank you for your response.
          Yes, I have define Q_OBJECT macro in all subclasses.
          Even though, I am not able to access the struct elements.
          Since, the above sample code provided is pseudo code, so I haven't mentioned all the details. sorry for that.
          I came across this below link from stack overflow but I am not sure wether Qt supports or not support exposing struct elements to QML
          https://stackoverflow.com/questions/7980900/qt-qml-c-qlist-of-structs-as-custom-listview-model#:~:text=QML cannot access "low-level,access these properties in QML.

          B Offline
          B Offline
          Bob64
          wrote on 7 Feb 2024, 13:53 last edited by
          #4

          @Praveen-Illa in the code you provided in your initial message, you did not show the Q_OBJECT macros. If you are defining them, that means we are not seeing the same code that you are using so it is difficult to see what you might be doing wrong.

          One thing I notice from your code is that you don't define deviceName as a Q_PROPERTY (see the answers in the StackOverflow link you mentioned). Is it the same in your real code?

          Another thing to mention is that if you are just exposing a simple struct, it might be worth looking into using Q_GADGET instead.

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          4 Feb 2024, 16:40

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