QWebEngineView Best Way to Wait for Asynchronous Data

kmbar2013

What is the best way to receive data if asynchronous? When the user clicks a QPushButton, I would like to query for data, however the runjavascript call takes too long to retrieve the data.

I have tried the following:

void MainWindow::getInformation()  // slot
{
    MyData data;
    m_webEngineView->executeCommand("getData(\'id_name\')");
    // problem is here because when the following call is made
    //  the data has not been updated yet
    data = m_webEngineView->getData();
}

Snippet from WebEngineView

void MyWebEngineView::executeCommand(QString cmd)
{
    page()->runJavaScript(cmd, myFunction);
}
void MyWebEngineView::myFunction(QVariant myvar)
{
    setData(myvar);
}
void MyWebEngineView::setData(QVariant myvar)
{
    // manipulate myvar to fill in m_data
    m_data = myvar.toMyData();
}
MyData MyWebEngine::getData()
{
    return m_data;
}

Thanks in advance for any help.

mcosta

Hi and welcome to devnet,

the problem is that you want a synchronous method MainWindow::getInformation() using asynchronous API.

My suggestion is to have a signal in your MyWebEngineView and emit it when the callback is executed

// MyWebEngineView.h
class MyWebEngineView:....
{
Q_SIGNALS:
    void dataReceived();
};

// MyWebEngineView.cpp
void MyWebEngineView::setData(QVariant myvar)
{
    m_data = myvar.toMyData();
    
    Q_EMIT dataReceived();
}

and then connect this signal to a slot in MainWindow

connect(m_webEngineView, &MyWebEngineView::dataReceived, this, &MainWindow::handleData);

void MainWindow::handleData()
{
    Mydata data = m_webEngineView->getData();

    // Use data
}

kmbar2013

@mcosta Your wording of my question was better. Thanks for the reply! I guess I was being lazy and hoping to avoid having 2 functions to call one. :-D