QAbstractListModel data to QML TableView why not shown through QQmlApplicationEngine

[kiwimess]

I want my data to be showed in QML in table. When I follow this example here: http://doc.qt.io/qt-5/qtquick-models...l-example.html and add the TableView and use QQuickView in main all data is showed fine.

import QtQuick 2.0
import QtQuick.Controls 1.2
 
Rectangle {
height: 300
width: 600
//![0]
    ListView {
        width: 200; height: 250
 
        model: myModel
        delegate: Text { text: "Animal: " + type + ", " + size }
    }
    //![0]
 
    TableView {
        y:150
        width: 600
        model: myModel
        TableViewColumn {
            role: "type"
            title: "Type"
            width: 200
        }
        TableViewColumn {
            role: "size"
            title: "Size"
            width: 200
        }
    }
}

import QtQuick 2.0
import QtQuick.Controls 1.2

Rectangle {
height: 300
width: 600
//![0]
    ListView {
        width: 200; height: 250

        model: myModel
        delegate: Text { text: "Animal: " + type + ", " + size }
    }
    //![0]

    TableView {
        y:150
        width: 600
        model: myModel
        TableViewColumn {
            role: "type"
            title: "Type"
            width: 200
        }
        TableViewColumn {
            role: "size"
            title: "Size"
            width: 200
        }
    }
}

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QGuiApplication app(argc, argv);
 
    AnimalModel model;
    model.addAnimal(Animal("Wolf", "Medium"));
    model.addAnimal(Animal("Polar bear", "Large"));
    model.addAnimal(Animal("Quoll", "Small"));
 
    QQuickView view;
    view.setResizeMode(QQuickView::SizeRootObjectToView);
    QQmlContext *ctxt = view.rootContext();
    ctxt->setContextProperty("myModel", &model);
//![0]
 
    view.setSource(QUrl("qrc:view.qml"));
    view.show();
 
    return app.exec();

QGuiApplication app(argc, argv);

    AnimalModel model;
    model.addAnimal(Animal("Wolf", "Medium"));
    model.addAnimal(Animal("Polar bear", "Large"));
    model.addAnimal(Animal("Quoll", "Small"));

    QQuickView view;
    view.setResizeMode(QQuickView::SizeRootObjectToView);
    QQmlContext *ctxt = view.rootContext();
    ctxt->setContextProperty("myModel", &model);
//![0]

    view.setSource(QUrl("qrc:view.qml"));
    view.show();

    return app.exec();

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But when I made my own implementation and wanted to use QQmlApplicationEngine, I get all the data fine to ListView but TableView is empty. And I just don't get it. Is it because of QQmlApplicationEngine or what?

Ok, this is not in main, it is in other classes constructor (doesn't make difference, does it?).

QQmlApplicationEngine *engine = new QQmlApplicationEngine;
 
    ComboModel combo;
    QStringList lst;
    lst << "Geelikynnet" << "Ripset" << "Kampaus" << "Tatuointi" << "Kulmat";
    combo.setComboList(lst);
 
    LineModel rokmodel;
    rokmodel.addLine(Line("Kulmat", "155,00", "Heidi"));
    rokmodel.addLine(Line("Tatuointi", "255,00", "Heidi"));
    rokmodel.addLine(Line("Kynnet", "55,00", "Ann-Marii"));
    rokmodel.addLine(Line("Ripset", "5,00", "Ann-Marii"));
 
    QQmlContext *ctxt = engine->rootContext();
    ctxt->setContextProperty("rokmodel", QVariant::fromValue(&rokmodel));
    ctxt->setContextProperty("myModel", QVariant::fromValue(combo.comboList()));
    ctxt->setContextProperty("comboModel", &combo);
    ctxt->setContextProperty("product", this);
 
    engine->load(QUrl(QStringLiteral("qrc:/main.qml")));
    QObject::connect(engine->rootObjects().takeFirst(), SIGNAL(qmlSignal(QString, QString)), this, SLOT(buttonPressed(QString, QString)));
    QObject::connect(engine->rootObjects().takeFirst(), SIGNAL(listSignal(QString)), this, SLOT(listSignal(QString)));

QQmlApplicationEngine *engine = new QQmlApplicationEngine;

    ComboModel combo;
    QStringList lst;
    lst << "Geelikynnet" << "Ripset" << "Kampaus" << "Tatuointi" << "Kulmat";
    combo.setComboList(lst);

    LineModel rokmodel;
    rokmodel.addLine(Line("Kulmat", "155,00", "Heidi"));
    rokmodel.addLine(Line("Tatuointi", "255,00", "Heidi"));
    rokmodel.addLine(Line("Kynnet", "55,00", "Ann-Marii"));
    rokmodel.addLine(Line("Ripset", "5,00", "Ann-Marii"));

    QQmlContext *ctxt = engine->rootContext();
    ctxt->setContextProperty("rokmodel", QVariant::fromValue(&rokmodel));
    ctxt->setContextProperty("myModel", QVariant::fromValue(combo.comboList()));
    ctxt->setContextProperty("comboModel", &combo);
    ctxt->setContextProperty("product", this);

    engine->load(QUrl(QStringLiteral("qrc:/main.qml")));
    QObject::connect(engine->rootObjects().takeFirst(), SIGNAL(qmlSignal(QString, QString)), this, SLOT(buttonPressed(QString, QString)));
    QObject::connect(engine->rootObjects().takeFirst(), SIGNAL(listSignal(QString)), this, SLOT(listSignal(QString)));

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I have very thin understanding about models, but I understood that QAbstractListModel is the best because the view is updated automatically if I add items to the list. ListView would be fine to me, but I dont get the text in columns.

[kiwimess]

It is not about QQmlApplicationEngine. Nor anything between TableView and QAbstractListModel. I made a simple test with Animal example and it showed everything ok.

So the problem must be in that I have many models. Or models are not ready somehow when qml loaded and the ListView gets updated afterwards and TableView isn't.

[anda_skoa]

You are not exporting rokmodel as an object but as a value. Are you sure you want to do that?

Btw, since you also export "this" as "product", why do those hacky connects at the end? Would be better to just handle the signals in QML.

Cheers,
_

[kiwimess]

I was just coming to tell that this was really a rookie mistake. Of course the data vanished in the end of constructor because of this: ComboModel combo; Changed it to pointer -> problem solved.

anda_skoa, do you mean using js in QML to handle signals? I'm having this Q_PROPERTY(QString sum READ sum WRITE setSum NOTIFY sumChanged) in my class and I change the product.sum value in QML from the class. I try to use only C++ and no js in this project.

Thanks for the help Anda.

[anda_skoa]

I meant something like this:

onListSignal: product.listSignal(nameOfSignalArgument)

onListSignal: product.listSignal(nameOfSignalArgument)

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I.e. using the QML signal handler and calling the C++ object's slot.

That way you don't need to make any assumptions in C++ on what the QML scene looks like (currently it assumes that the first object has those signals).

Cheers,
_

[kiwimess]

Ok, I am doing just that to find out which line clicked:

onClicked: applicationWindow.listSignal(tableView.currentRow)

onClicked: applicationWindow.listSignal(tableView.currentRow)

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Product is different. It is meant to change the sum text in QML from C++.

[anda_skoa]

I see.

Then you could just do

onClicked: product.listSignal(tableView.currentRow)

onClicked: product.listSignal(tableView.currentRow)

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i.e. calling the slot "listSignal" on object "product" directly.

Cheers,
_

[kiwimess]

I have one more question to you, if you like to help a bit more...

When I run this in my testprogram main, it shows line data ok.

LineModel model;
 
model.addLine(Line("Candy", "Ben", "10"));
model.addLine(Line("Paper", "Ben", "20"));
model.addLine(Line("Matches", "Ben", "30"));
 
QQmlApplicationEngine *engine = new QQmlApplicationEngine;
QQmlContext *ctxt = engine->rootContext();
ctxt->setContextProperty("myModel", &model);
engine->load(QUrl(QStringLiteral("qrc:/main.qml")));
 
Line line = model.get(1);
qDebug() << line.article();
qDebug() << line.person();
qDebug() << line.price();

LineModel model;

model.addLine(Line("Candy", "Ben", "10"));
model.addLine(Line("Paper", "Ben", "20"));
model.addLine(Line("Matches", "Ben", "30"));

QQmlApplicationEngine *engine = new QQmlApplicationEngine;
QQmlContext *ctxt = engine->rootContext();
ctxt->setContextProperty("myModel", &model);
engine->load(QUrl(QStringLiteral("qrc:/main.qml")));

Line line = model.get(1);
qDebug() << line.article();
qDebug() << line.person();
qDebug() << line.price();

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But when I run it from in my another programs class where linemodel is (now) member value (I hope this is said right).
Now the program crashes, when run this function.

.h:
LineModel *linemodel;
Line *oneline;
 
class:
//Line *oneline = new Line;
Line oneline = linemodel->get(1);
qDebug() << oneline.article();

.h:
LineModel *linemodel;
Line *oneline;

class:
//Line *oneline = new Line;
Line oneline = linemodel->get(1);
qDebug() << oneline.article();

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And the get, which is the same in working and not working programs.

Line LineModel::get(int index) const 
{
    const Line line = m_lines[index];
    return line;
}

Line LineModel::get(int index) const 
{
    const Line line = m_lines[index];
    return line;
}

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[anda_skoa]

is the linemodel pointer valid?
Is the index valid?

Cheers,
_

[kiwimess]

h:
private: Linemodel *linemodel; Line *oneline;
 
constructor:
LineModel *linemodel = new LineModel;
linemodel->addLine(Line("Book", "1,40", "Heidi"));
linemodel->addLine(Line("Paper", "2,40", "Heidi"));
linemodel->addLine(Line("Pen", "12,40", "Heidi"));

h:
private: Linemodel *linemodel; Line *oneline;

constructor:
LineModel *linemodel = new LineModel;
linemodel->addLine(Line("Book", "1,40", "Heidi"));
linemodel->addLine(Line("Paper", "2,40", "Heidi"));
linemodel->addLine(Line("Pen", "12,40", "Heidi"));

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And here in beginning of line 1. debugger says that "linemodel not accessible". Doesn't the *linemodel in constructor hold the data? And the private members are available to everywhere inside that class? This is inside a slot (shouldn't make any difference?)

Line oneline = linemodel->get(0);
qDebug() << oneline.article();

Line oneline = linemodel->get(0);
qDebug() << oneline.article();

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[anda_skoa]

[QUOTE=kiwimess;281990]

constructor:
LineModel *linemodel = new LineModel;

constructor:
LineModel *linemodel = new LineModel;

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If you really have that in your constructor then you have the "linemodel" member uninitialized.

And the private members are available to everywhere inside that class?

Yes.
But if you code above is actually what you have, then you are not accessing the member but shadowing it with a local variable.

Cheers,
_

[kiwimess]

So now when I have LineModel *linemodel in header as private member, I need to make a function to pass it as reference to be used in main. And this way all the data is usable in this class later? Sorry for simple questions, I'm simple person

[anda_skoa]

As a pointer, since you need a pointer to export it as a context property.

But you better post updated code, otherwise we might be talking about very different things.

Cheers,
_

[kiwimess]

You read my mind, I was thinking the same.
Actually what I'm trying to do is add and remove lines from the list in c++. And hope that list updates itself automaticly in QML.

class CashRegister : public QObject
{
    Q_OBJECT
    Q_PROPERTY(QString sum READ sum WRITE setSum NOTIFY sumChanged)
public:
    explicit CashRegister(QObject *parent = 0);
    QString sum();
    void setSum(QString sum);
signals:
    void sumChanged();
public slots:
    void buttonPressed(const QString &type, const QString &id);
    void listSignal(const QString &index);
private:
    QQmlApplicationEngine *engine;
    QList<QObject*> dataList;
    QString m_sum;
    QString userName;
    QQmlContext *ctxt;
    LineModel *linemodel;        // SHOULNT THIS SAVE THE DATA?
};

class CashRegister : public QObject
{
    Q_OBJECT
    Q_PROPERTY(QString sum READ sum WRITE setSum NOTIFY sumChanged)
public:
    explicit CashRegister(QObject *parent = 0);
    QString sum();
    void setSum(QString sum);
signals:
    void sumChanged();
public slots:
    void buttonPressed(const QString &type, const QString &id);
    void listSignal(const QString &index);
private:
    QQmlApplicationEngine *engine;
    QList<QObject*> dataList;
    QString m_sum;
    QString userName;
    QQmlContext *ctxt;
    LineModel *linemodel;        // SHOULNT THIS SAVE THE DATA?
};

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CashRegister::CashRegister(QObject *parent) : QObject(parent)
{
    QQmlApplicationEngine *engine = new QQmlApplicationEngine;
    ComboModel combo;
    QStringList lst;
    lst << "Book" << "Pen" << "Eraser" << "Liner" << "Notebook";
    combo.setComboList(lst);
 
// TODO: dataList omaan luokkaa pois tästä luokasta
 
    LineModel *linemodel = new LineModel;
    linemodel->addLine(Line("Book", "1,40", "Heidi"));
    linemodel->addLine(Line("Paper", "2,40", "Heidi"));
    linemodel->addLine(Line("Pen", "12,40", "Heidi"));
 
    QQmlContext *ctxt = engine->rootContext();
    ctxt->setContextProperty("rokmodel", linemodel);
    ctxt->setContextProperty("myModel", QVariant::fromValue(combo.comboList()));
    ctxt->setContextProperty("comboModel", &combo);
    ctxt->setContextProperty("product", this);
 
    engine->load(QUrl(QStringLiteral("qrc:/main.qml")));
 
    QObject::connect(engine->rootObjects().takeFirst(), SIGNAL(qmlSignal(QString, QString)), this, SLOT(buttonPressed(QString, QString)));
    QObject::connect(engine->rootObjects().takeFirst(), SIGNAL(listSignal(QString)), this, SLOT(listSignal(QString)));
 
    Line oneline = linemodel->get(0);
    qDebug() << oneline.article();
}

CashRegister::CashRegister(QObject *parent) : QObject(parent)
{
    QQmlApplicationEngine *engine = new QQmlApplicationEngine;
    ComboModel combo;
    QStringList lst;
    lst << "Book" << "Pen" << "Eraser" << "Liner" << "Notebook";
    combo.setComboList(lst);

// TODO: dataList omaan luokkaa pois tästä luokasta

    LineModel *linemodel = new LineModel;
    linemodel->addLine(Line("Book", "1,40", "Heidi"));
    linemodel->addLine(Line("Paper", "2,40", "Heidi"));
    linemodel->addLine(Line("Pen", "12,40", "Heidi"));

    QQmlContext *ctxt = engine->rootContext();
    ctxt->setContextProperty("rokmodel", linemodel);
    ctxt->setContextProperty("myModel", QVariant::fromValue(combo.comboList()));
    ctxt->setContextProperty("comboModel", &combo);
    ctxt->setContextProperty("product", this);

    engine->load(QUrl(QStringLiteral("qrc:/main.qml")));

    QObject::connect(engine->rootObjects().takeFirst(), SIGNAL(qmlSignal(QString, QString)), this, SLOT(buttonPressed(QString, QString)));
    QObject::connect(engine->rootObjects().takeFirst(), SIGNAL(listSignal(QString)), this, SLOT(listSignal(QString)));

    Line oneline = linemodel->get(0);
    qDebug() << oneline.article();
}

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Here last two lines work ok.

But when used in code below -> explosion.

void CashRegister::buttonPressed(const QString &type, const QString &id) {
    qDebug() << "Called the C++ slot with message:" << type << id;
- - - -
    else if(type == "add") {
        qDebug() << "add pressed!";
        //Line *oneline = new Line;
        Line oneline = linemodel->get(0);
        qDebug() << oneline.article();
        return;
    }
- - - -

void CashRegister::buttonPressed(const QString &type, const QString &id) {
    qDebug() << "Called the C++ slot with message:" << type << id;
- - - -
    else if(type == "add") {
        qDebug() << "add pressed!";
        //Line *oneline = new Line;
        Line oneline = linemodel->get(0);
        qDebug() << oneline.article();
        return;
    }
- - - -

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So this last linemodel (7.) is not the same than in constructor (and I know answer is not very compilated but my matches are wet).

[anda_skoa]

In CashRegister::buttonPressed() you are accessing the member "linemodel", which is never initialized.
An uninitialized pointer can point to anywhere, in most cases any attempt to access it will cause a crash.

Your problem, as pointed out earlier, is in line 11 of your constructor.
Instead of using a local variable, it should be initializing the member.

Cheers,
_

[kiwimess]

linemodel = new LineModel;

linemodel = new LineModel;

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It works! (I'm dancing here )
Thank you very much Anda for your help!