How to display a QAbstractListModel in qml?

[mjs225]

I want to display a QAbstractListModel in qml. I create a simple app but fails to make it work. The window is empty and the model is not accessed from qml. Please help point out what's wrong with this code.

// main.cpp
#include <QAbstractListModel>
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>

struct Model : QAbstractListModel {
  QStringList lst{"txt1", "txt2", "txt3"};

  int rowCount(const QModelIndex &parent) const override {
    // never called
    if (parent.isValid())
      return 0;
    return lst.length();
  }
  QVariant data(const QModelIndex &index, int role) const override {
    // never called
    if (index.row() < 0 || index.row() >= lst.size())
      return QVariant{};
    if (role == Qt::DisplayRole)
      return lst.at(index.row());
    return QVariant{};
  }
};

int main(int argc, char *argv[]) {
  QGuiApplication app{argc, argv};
  Model model;
  QQmlApplicationEngine engine;
  QObject::connect(
      &engine, &QQmlApplicationEngine::objectCreationFailed, &app,
      []() { QCoreApplication::exit(-1); }, Qt::QueuedConnection);
  QQmlContext *context = engine.rootContext();
  context->setContextProperty("model", &model);
  // doesn't work: engine.setInitialProperties({{"model",
  // QVariant::fromValue(&model)}});

  engine.loadFromModule("app", "Main");
  return app.exec();
}

import QtQuick
import QtQuick.Controls
ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: "App"

    ListView {
        id: listView
        anchors.fill: parent
        model: model

        delegate: Item {
            width: listView.width
            height: 50

            Text {
                anchors.centerIn: parent
                text: model.display
            }
        }
    }
}

[mjs225]

@jeremy_k said in How to display a QAbstractListModel in qml?:

@mjs225 said in How to display a QAbstractListModel in qml?:

I want to display a QAbstractListModel in qml. I create a simple app but fails to make it work. The window is empty and the model is not accessed from qml. Please help point out what's wrong with this code.

// main.cpp
  // doesn't work: engine.setInitialProperties({{"model",
  // QVariant::fromValue(&model)}});

The top level component doesn't have a model property, and setInitialProperties doesn't recursively search subcomponents to apply to.

ApplicationWindow {

    ListView {
        id: listView
        anchors.fill: parent
        model: model
    }
}

The right side of model: model within listView is going to resolve to listView.model, ie itself.

Thanks. I find 2 fixes based on the suggestion:

• Rename the property "model".
  in C++: context->setContextProperty("mymodel", &model);
  in qml: ListView { model: mymodel }
• in C++: replace context->setContextProperty("model", &model); with engine.setInitialProperties({{"model", QVariant::fromValue(&model)}});
  in qml: Add property var model and id: appWindow to top level component. Use model: appWindow.model in ListView

[jeremy_k]

@mjs225 said in How to display a QAbstractListModel in qml?:

I want to display a QAbstractListModel in qml. I create a simple app but fails to make it work. The window is empty and the model is not accessed from qml. Please help point out what's wrong with this code.

// main.cpp
  // doesn't work: engine.setInitialProperties({{"model",
  // QVariant::fromValue(&model)}});

The top level component doesn't have a model property, and setInitialProperties doesn't recursively search subcomponents to apply to.

ApplicationWindow {

    ListView {
        id: listView
        anchors.fill: parent
        model: model
    }
}

The right side of model: model within listView is going to resolve to listView.model, ie itself.

[mjs225]

@jeremy_k said in How to display a QAbstractListModel in qml?:

@mjs225 said in How to display a QAbstractListModel in qml?:

I want to display a QAbstractListModel in qml. I create a simple app but fails to make it work. The window is empty and the model is not accessed from qml. Please help point out what's wrong with this code.

// main.cpp
  // doesn't work: engine.setInitialProperties({{"model",
  // QVariant::fromValue(&model)}});

The top level component doesn't have a model property, and setInitialProperties doesn't recursively search subcomponents to apply to.

ApplicationWindow {

    ListView {
        id: listView
        anchors.fill: parent
        model: model
    }
}

The right side of model: model within listView is going to resolve to listView.model, ie itself.

Thanks. I find 2 fixes based on the suggestion:

• Rename the property "model".
  in C++: context->setContextProperty("mymodel", &model);
  in qml: ListView { model: mymodel }
• in C++: replace context->setContextProperty("model", &model); with engine.setInitialProperties({{"model", QVariant::fromValue(&model)}});
  in qml: Add property var model and id: appWindow to top level component. Use model: appWindow.model in ListView