It's possible to call c++ function from qml and update a ListModel?

sdsoldi

I'm trying to update my ListModel but it is impossible.

If I set on my main.cpp

QStringList dataList;
dataList.append("Item 222");
QQmlContext *ctxt = engine.rootContext();
ctxt->setContextProperty("myModel",  QVariant::fromValue(dataList));

It's working.

But if a do the same on a excel.h doesn't work

QStringList dataList;
dataList.append("Item 222");
QQmlApplicationEngine engine;
QQmlContext *classContext = engine.rootContext();
classContext->setContextProperty("myModel", QVariant::fromValue(dataList));

It is not updating my combobox.

I need to open a excel and set combobox items but I can't.

Thanks and sorry for my bad english

sierdzio

This is described in depth in the documentation: link

Quoting:

Note: There is no way for the view to know that the contents of a QStringList have changed. If the QStringList changes, it will be necessary to reset the model by calling QQmlContext::setContextProperty() again.

sierdzio

Hm actually you are calling setContextProperty() again, so it should work. Are you sure you are updating correct model ("myModel" - is it correct)?

sdsoldi

@sierdzio Yep because if I do on Main.cpp it's working. But when I call from qml to this function on excel.h doesn't work.

No errors, and no info on debugger.

Also I've got a

qmlRegisterType<Excel>("com.myself", 1, 0, "Excel");

line on main.cpp to call those functions on excel.h

vladstelmahovsky

Have thought about your list gets out of scope?
Cant see full sources, so cant say 100% sure, but it looks like it is

sdsoldi

I feel the delay in answering...

I can't paste my code here... I have this error message when I post it: Post content was flagged as spam by Akismet.com

Edit:

I suppose that I need "refresh" main.qml or reload it.

Here is my main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QtQml>

#include "Excel.h"

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    qmlRegisterType<Excel>("com.myself", 1, 0, "Excel");

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

    QStringList dataList;
    dataList.append("wololo");

    engine.rootContext()->setContextProperty( "cppModel", QVariant::fromValue(dataList) );

    return app.exec();
}

Class of excel file. I'm loading xlsxdocument plugin.
Excel.h

#ifndef EXCEL_H
#define EXCEL_H

#include <QObject>
#include "xlsx/xlsxdocument.h"
#include "xlsx/xlsxabstractsheet.h"

class Excel : public QObject
{
    Q_OBJECT
public:
    Q_INVOKABLE getExcel(QString path);

signals:

public slots:
};

#endif // EXCEL_H

Here is my function that I'm trying to update my combobox model.
Excel.cpp

#include "Excel.h"
#include <QDebug>
#include <QQmlApplicationEngine>
#include <QtQml>

Excel::getExcel(QString path)
{
    path.remove(0,8);
    qDebug() << path;
    QXlsx::Document xlsx(path);
    xlsx.selectSheet("MOULD DIMENSIONS");
    //etc..

    QQmlApplicationEngine engine;
    QStringList dataList;
    dataList.append("Item 2");
    engine.rootContext()->setContextProperty( "cppModel", QVariant::fromValue(dataList) );
}

And here is my main qml.
main.qml

import QtQuick 2.5
import QtQuick.Window 2.2
import QtQuick.Controls 1.4
import QtQuick.Dialogs 1.2
import com.myself 1.0


Window {
    visible: true

    Excel {
        id: excel
    }

    Button {
        id: btnOpen
        width: 125
        text: qsTr("Open Excel")
        clip: false
    }

    ComboBox {
        id: combo
        model: cppModel
    }

    FileDialog {
        id: fileDialog
        title: "Please choose a file"
        folder: shortcuts.home
        onAccepted: {
            excel.getExcel(fileDialog.fileUrls.toString());

        }
    }
    Connections {
        target: btnOpen
        onClicked: fileDialog.visible = true
    }
}

When I run, the combobox has only 1 item. 'wololo' item.
And when I open a Excel file, I need to change the combobox items. In this example I need to add 'Item 2' item to combobox.

But is not working.

sierdzio

The 'engine' you create in getExcel() is not the same object as the one you create in main.cpp... so you are setting the root property on a different engine than the one you use to display QML :-)

To fix this, just pass the engine (or the root context) pointer to your Excel class and use it in getExcel().

sierdzio

Another option is to use parent-child hierarchy instead of root properties.

So, in QML:

Excel {
  ComboBox {
    id: combo
    objectName: "combo"
  }
}

And then set model from CPP:

// Pseudocode, written from memory. Please check the docs to be sure:
QObject *combo = findChildren<QQuickItem*>("combo"); // combo is a child of Excel in QML!
if (combo) {
  combo->setProperty("model", QVariant::fromValue(dataList) );
}

Not sure which one you'll find more aesthetic (also not sure if the second option would work at all ;-) ).

sdsoldi

@sierdzio said:

The 'engine' you create in getExcel() is not the same object as the one you create in main.cpp... so you are setting the root property on a different engine than the one you use to display QML :-)

To fix this, just pass the engine (or the root context) pointer to your Excel class and use it in getExcel().

Oh!! It's true... I supose that If I create a engine on main, I can use It on another cpp or h class...

But now I have a another question... How I can pass engine, or root from main to qml and them from qml to function?

Anyway, I will try the parent-child

sierdzio

@sdsoldi said:

How I can pass engine, or root from main to qml and them from qml to function?

You can create a singleton class in C++, pass the engine pointer to it in main.cpp, and then simply access it in your Excel class. This is probably the simplest solution, although singletons do have their drawbacks.

Or add the engine as a context property to QML, then assign it to Excel object... although that seems awkward.

vladstelmahovsky

or use
QQmlEngine *qmlEngine(const QObject *object)

sdsoldi

@vladstelmahovsky Can you explain it please?

sierdzio

@sdsoldi

It is a static method of the engine. SO you can probably use it like this (in Excel class):

    QQmlEngine *engine = qmlEngine(this); // because "this" is an item you have added to QML
    QStringList dataList;
    dataList.append("Item 2");
    engine.rootContext()->setContextProperty( "cppModel", QVariant::fromValue(dataList) );

sdsoldi

@sierdzio @vladstelmahovsky
Oh my god! It's as simple as that...

Thank you very much!

vladstelmahovsky

yep, but dont forget to check for null