Updating c++ data in Qml

[dziko147]

@jsulm this is my situation.

My project compouned of 3 classes :
1/Mainwindow
2/backend
/UploadCSV
In Mainwindow :
1/ I have a quickwidget which integrate a qml file .
2/ I create a backend instance to get data from it and fill the QMl File

In Backend
1/I have the defenition of my data (getter, setter, change slots).

In UploadCSV
1/I have a button when it's clicked a slot in Backend will change some data .
2/After change data I would like to display it on QML .

I hope it's clear

[jsulm]

@dziko147 said in Updating c++ data in Qml:

I hope it's clear

No, you did not answer my question, which is actually quite clear...

[dziko147]

I give uuuuuuuuuuuuuup

[J.Hilk]

alright @jsulm

@dziko147 this does actually help

My project compouned of 3 classes :
1/Mainwindow
2/backend
/UploadCSV
In Mainwindow :
1/ I have a quickwidget which integrate a qml file .
2/ I create a backend instance to get data from it and fill the QMl File

In Backend
1/I have the defenition of my data (getter, setter, change slots).

In UploadCSV
1/I have a button when it's clicked a slot in Backend will change some data .
2/After change data I would like to display it on QML .

I hope it's clear

some more required information:

• how do you expose backend to the qml context, and where (in your code)
• name of your backend and uploadcsv instances, and where they are defined
• does UploadCSV have its own UI components? do you mean that with "button"

I have the high suspicion that everything is centered in and around mainwindow already and its only a matter of connecting it. But truthfully code will help, it doesn't look like you have much yet, so post as much as you can

[dziko147]

@J-Hilk
1/ I expose backend to qml like this :

back= new Backend();
    m_ui->quickWidget->setVisible(true);
    m_ui->quickWidget->rootContext()->setContextProperty("cppObject",back);
    m_ui->quickWidget->setResizeMode(QQuickWidget::SizeRootObjectToView);
    m_ui->quickWidget->setSource(QUrl(QStringLiteral("qrc:/qml/automotive.qml")));

2/ And UploadCSV in MainWindow just for show . I dont use UploadCSV in MainWindow

//BTW CAN i define the connect signal of UploadCSV button here ?
void MainWindow::on_actionUpload_CSV_File_triggered()
{
    uploadcsv = new UploadCSV();
    uploadcsv->show();
}

3/ Yes Sure UploadCSV has a UI form .

[J.Hilk]

@dziko147 alright,

we are getting closer,

I assume this:

back= new Backend();
    m_ui->quickWidget->setVisible(true);
    m_ui->quickWidget->rootContext()->setContextProperty("cppObject",back);
    m_ui->quickWidget->setResizeMode(QQuickWidget::SizeRootObjectToView);
    m_ui->quickWidget->setSource(QUrl(QStringLiteral("qrc:/qml/automotive.qml")));

is inside the MainWindow constructor ?

//BTW CAN i define the connect signal of UploadCSV button here ?
void MainWindow::on_actionUpload_CSV_File_triggered()
{
    uploadcsv = new UploadCSV();
    uploadcsv->show();
}

The way you have it currently set up, you have to make the connect call here.

but that won't work quite yet.

• I assume the button you want to press, to update your backend is part of the UploadCSV ui ? Therefore ui->parambtn_2 is the button you want to press and is part of the UploadCSV ui?
• have you yet defined a (custom)signal inside the UploadCSV class ?

[J.Hilk]

If my assumptions are correct, I'm writing this before a response,

you can/should make the following changes:

inside UploadCSV .h add a custom signal, for example purpose we'll name it myCustomButtonClicked(),

public:
    explicit UploadCSV(QObject *parent = nullptr);
.....

signals:
      void myCustomButtonClicked();

inside UploadCSV.cpp constructor definition, after ui->setupUi(this), connect the button to the recently created signal:

{
    ui->setupUi(this);
    connect(ui->parambtn_2, &QAbstractButton::clicked, this, &UploadCSV::myCustomButtonClicked); // this connects/forwards the button clicked signal to the  class signal 'myCustomButtonClicked'
}

in mainwindow constructor, instantiate the UploadCSV in the constructor and connect it to the backend:

{
    ui->setupUi(this);
back= new Backend();
    m_ui->quickWidget->setVisible(true);
    m_ui->quickWidget->rootContext()->setContextProperty("cppObject",back);
    m_ui->quickWidget->setResizeMode(QQuickWidget::SizeRootObjectToView);
    m_ui->quickWidget->setSource(QUrl(QStringLiteral("qrc:/qml/automotive.qml")));

uploadcsv = new UploadCSV();
connect(uploadcsv, & UploadCSV:: myCustomButtonClicked, backend, &Backend::status); //status has to be public!

}

your on_actionUpload_CSV_File_triggered now only contains this:

void MainWindow::on_actionUpload_CSV_File_triggered()
{
    uploadcsv->show();
}

let's see if that worked.

code my contain typos, so be aware :D

[dziko147]

@J-Hilk said in Updating c++ data in Qml:

If my assumptions are correct, I'm writing this before a response,

Finally it works :D :D :D

[dziko147]

And thanks @KroMignon @jsulm thank you for the effort you made for me

[J.Hilk]

@dziko147 WUHUH congrats!

If you would be so kind and use the topic tool button and set the topic to solved :D