Accessing C++ Model via QML throws error: ListElement: cannot use script for property

[4k]

I want to be able to access member variables of a C++ Model via QML

I have a ListModel:

ListModel {
        id: credentialsModel
       ListElement {
            UserName: myCredentials.getUser
            Password: myCredentials.getPassword
        }
    }

ListModel {
        id: credentialsModel
       ListElement {
            UserName: myCredentials.getUser
            Password: myCredentials.getPassword
        }
    }

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Which I am trying to fill with members of a class MyCredentials:

#ifndef MYCREDENTIALS_H
#define MYCREDENTIALS_H
 
#pragma once
 
#include <iostream>
#include <QObject>
 
class MyCredentials: public QObject
{
    Q_OBJECT
    Q_PROPERTY(std::string* getUser READ getUser WRITE setUser)
    Q_PROPERTY(std::string* getPassword READ getPassword WRITE setPassword)
 
        public:
        explicit MyCredentials(std::string* user, std::string* password, QObject *parent = nullptr): m_user(user),m_password(password) {};
 
        void print() const{
            std::cout<<"user "<<*m_user<<std::endl;
            std::cout<<"password "<<*m_password<<std::endl;
            std::cout.flush();
        }
 
        std::string* getUser() const
        {
            return m_user;
        }
 
        void setUser(std::string* value)
        {
            m_user = value;
        }
 
        std::string* getPassword() const
        {
            return m_password;
        }
 
        void setPassword(std::string* value)
        {
            m_password = value;
        }
 
        private:
            std::string* m_user;
            std::string* m_password;
};
 
#endif // MYCREDENTIALS_H

#ifndef MYCREDENTIALS_H
#define MYCREDENTIALS_H

#pragma once

#include <iostream>
#include <QObject>

class MyCredentials: public QObject
{
    Q_OBJECT
    Q_PROPERTY(std::string* getUser READ getUser WRITE setUser)
    Q_PROPERTY(std::string* getPassword READ getPassword WRITE setPassword)

        public:
        explicit MyCredentials(std::string* user, std::string* password, QObject *parent = nullptr): m_user(user),m_password(password) {};

        void print() const{
            std::cout<<"user "<<*m_user<<std::endl;
            std::cout<<"password "<<*m_password<<std::endl;
            std::cout.flush();
        }

        std::string* getUser() const
        {
            return m_user;
        }

        void setUser(std::string* value)
        {
            m_user = value;
        }

        std::string* getPassword() const
        {
            return m_password;
        }

        void setPassword(std::string* value)
        {
            m_password = value;
        }

        private:
            std::string* m_user;
            std::string* m_password;
};

#endif // MYCREDENTIALS_H

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This ListModel is inside a main.qml:

import QtQuick 2.12
import QtQuick.Controls 2.5
 
ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Tabs")
 
    ListModel {
       id: credentialsModel
       ListElement {
 
          // Thats my goal: I want to get member variables of the ContextProperty myList
          // Why this error?: ListElement: cannot use script for property value
          UserName: myCredentials.getUser
          Password: myCredentials.getPassword
       }
    }
 
    SwipeView {
        id: swipeView
        anchors.fill: parent
        currentIndex: tabBar.currentIndex
 
        CredentialsView{
            id: dataBasesView
 
        }
    }
 
    footer: TabBar {
        id: tabBar
        currentIndex: swipeView.currentIndex
 
        TabButton {
            text: qsTr("Credentials")
        }
    }
}

import QtQuick 2.12
import QtQuick.Controls 2.5

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Tabs")

    ListModel {
       id: credentialsModel
       ListElement {

          // Thats my goal: I want to get member variables of the ContextProperty myList
          // Why this error?: ListElement: cannot use script for property value
          UserName: myCredentials.getUser
          Password: myCredentials.getPassword
       }
    }

    SwipeView {
        id: swipeView
        anchors.fill: parent
        currentIndex: tabBar.currentIndex

        CredentialsView{
            id: dataBasesView

        }
    }

    footer: TabBar {
        id: tabBar
        currentIndex: swipeView.currentIndex

        TabButton {
            text: qsTr("Credentials")
        }
    }
}

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Inside this main.qml a SwipeView with an component CredentialsView is used:

import QtQuick 2.9
import QtQuick.Controls 2.2
import QtQuick.Layouts 1.3
 
Page {
    id: page
    width: 600
    height: 400
 
    header: Label {
        text: qsTr("Credentials")
        font.pixelSize: Qt.application.font.pixelSize * 2
        padding: 10
    }
 
    CredentialsTableView{
        anchors.fill: parent
        model: credentialsModel
    }
 
}

import QtQuick 2.9
import QtQuick.Controls 2.2
import QtQuick.Layouts 1.3

Page {
    id: page
    width: 600
    height: 400

    header: Label {
        text: qsTr("Credentials")
        font.pixelSize: Qt.application.font.pixelSize * 2
        padding: 10
    }

    CredentialsTableView{
        anchors.fill: parent
        model: credentialsModel
    }

}

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The component CredentialsView contains a TableView:

import QtQuick 2.9
import QtQuick.Controls 1.4
import QtQuick.Layouts 1.3
 
TableView {
    id: credentialsTableView
    TableViewColumn {
        role: "UserName"
        title: "User Name"
        width: credentialsTableView.width / 2
    }
    TableViewColumn {
        role: "Password"
        title: "Password"
        width: credentialsTableView.width / 2
    }
}

import QtQuick 2.9
import QtQuick.Controls 1.4
import QtQuick.Layouts 1.3

TableView {
    id: credentialsTableView
    TableViewColumn {
        role: "UserName"
        title: "User Name"
        width: credentialsTableView.width / 2
    }
    TableViewColumn {
        role: "Password"
        title: "Password"
        width: credentialsTableView.width / 2
    }
}

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main.cpp:

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
 
#include "mycredentials.h"
 
int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
 
    QGuiApplication app(argc, argv);
 
    std::string* myUser;
    std::string user("usr");
    myUser = &user;
 
    std::string* myPassword;
    std::string password("psw");
    myPassword = &password;
 
    MyCredentials myCredentials(myUser, myPassword);
 
    myCredentials.print();
 
    QQmlApplicationEngine engine;
    engine.rootContext()->setContextProperty(QStringLiteral("myCredentials"), &myCredentials);
 
    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);
    engine.load(url);
 
    return app.exec();
}

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>

#include "mycredentials.h"

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

    QGuiApplication app(argc, argv);

    std::string* myUser;
    std::string user("usr");
    myUser = &user;

    std::string* myPassword;
    std::string password("psw");
    myPassword = &password;

    MyCredentials myCredentials(myUser, myPassword);

    myCredentials.print();

    QQmlApplicationEngine engine;
    engine.rootContext()->setContextProperty(QStringLiteral("myCredentials"), &myCredentials);

    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);
    engine.load(url);

    return app.exec();
}

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Code is available via https://github.com/hstig/qt.

Where is my error? What should I do?

Many thanks

[peppermg]

QML doesn't know what std::string* is. https://doc.qt.io/qt-5/qtqml-cppinte...-qt-data-types

[4k]

QML doesn't know what std::string* is. https://doc.qt.io/qt-5/qtqml-cppinte...-qt-data-types

Thanks, but same error with QString*. I think there is no way to use the static ListElement in QML. Maybe it is not allowed to change the values inside ListModel: https://www.ics.com/webinar/vbhdsgjashgd at Minute 3:35. Or is it possible somehow anyway?

[peppermg]

It also won't know what a QString * is, don't use pointers here. I am not sure what your end goal is with this, but look at sub-classing QAbstractListModel. https://doc.qt.io/qt-5/qtquick-model...model-subclass