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Dynamic qml object creation from c++ code



  • I want to strongly separate app logic on c++ and gui on qt quick. I have map (2d array) of cells with deferent properties, which will be modified during app lifecycle. Size of map also can vary. I have cell.qml that describes how cell should look like. But i don't understand how to dynamically create certain amout of cells in qml from cpp code. For example, at initialization, when i create c++ object i need corresponding qml object to be created as well.



  • Hello @FedorKozlov.

    From my point of view, if you want to trigger an action from the c++ side to qml side, you must use the signal/slot mechanism. Otherwise, you should have the object of your c++ class in qml, and if the user triggers an event, you provide a method to respond that action if it is required backend activity.

    If you provide some code it would nice, your explication it is kind of abstract.


  • Qt Champions 2018

    For your usecase you should expose a QAbstractItemModel to your QML layer.
    Then in QML you would use a Repeater that will instantiate a Cell for each row of your model.



  • @FedorKozlov
    It's much easier to do QML tasks in QML. Create a QML method to do it and call it from C++ with QMetaObject::invokeMethod().



  • Thank you all for your answers!

    I believe as @GrecKo said QAbstractItemModel is what i really need.
    Though, as i found here http://doc.qt.io/qt-5/qtquick-modelviewsdata-cppmodels.html
    QAbstractItemModel presents a hierarchy of tables, but the views currently provided by QML can only display list data. In order to display the child lists of a hierarchical model, use the DelegateModel QML type


  • Qt Champions 2018

    @FedorKozlov There's no need for a DelegateModel in your case.

    You can display table data with a TableView, but you can also display data in a table like fashion with a GridView or even a Repeater with the delegates positionning themselves.

    If I guessed right you are trying to do some kind of Game of Life in Qt Quick.
    The position of your cells is just data, you don't really need a table model.



  • @GrecKo You're right! I am defenetly doing some kind of Game of Life)
    I've managed to create a map, using GridView and QAbstractListModel like in this video.
    I also understood how to pass values using model's roles. Now I'm trying to find out how to pass user defined classes through QVariant. I guess i also should register my 'Cell' class with qmlRegisterType<>


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