TypeError: Property '' of object QObject(0x6cfdf0) is not a function

[davidesalvetti]

Hi,

I'm following an example on how to connect qml and c++. ( this is the link of the example chapter Q_INVOKABLE).
My program is the following:

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include "receiver.h"

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

    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    Receiver rcvr;
    engine.rootContext()->setContextProperty("Receiver", &rcvr);
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    if (engine.rootObjects().isEmpty())
        return -1;

    return app.exec();
}

Receiver.h

#include <QObject>
#include <QDebug>
class Receiver : public QObject
{
public:
    Receiver();
    Q_INVOKABLE bool postMessage(const QString &msg) {
            qDebug() << "Called the C++ method with" << msg;
            return true;
        }
};

main.qml

import QtQuick 2.9
import QtQuick.Controls 2.2

ApplicationWindow {
    id: window
    visible: true
    width: 640
    height: 480
    title: qsTr("Stack")

    header: ToolBar {
        contentHeight: toolButton.implicitHeight

        ToolButton {
            id: toolButton
            text: /*stackView.depth > 1 ? "\u25C0" :*/ "\u2630"
            font.pixelSize: Qt.application.font.pixelSize * 1.6
            onClicked: {
//                if (stackView.depth > 1) {
//                    stackView.pop()
//                } else {
                    drawer.open()
                var result = Receiver.postMessage("Hello from QML")
                console.log("Result of postMessage():", result)
//                }

            }
        }

        Label {
            text: stackView.currentItem.title
            anchors.centerIn: parent
        }
    }

    Drawer {
        id: drawer
        width: window.width * 0.66
        height: window.height

        Column {
            anchors.fill: parent

            ItemDelegate {
                text: qsTr("Page 1")
                width: parent.width
                onClicked: {
                    stackView.push("Page1Form.ui.qml")
                    drawer.close()
                }
            }
            ItemDelegate {
                text: qsTr("Page 2")
                width: parent.width
                onClicked: {
                    stackView.push("Page2Form.ui.qml")
                    drawer.close()
                }
            }
        }
    }

    StackView {
        id: stackView
        initialItem:"Page1Form.ui.qml"//"HomeForm.ui.qml"
        anchors.fill: parent
    }
}

Now when I click on the toolbar I try to call the function on Receiver.h I get this error:
"qrc:/main.qml:23: TypeError: Property 'postMessage' of object QObject(0x6cfdf0) is not a function"

Anybody knows what I'm doing wrong here? Thanks in advance!

[ODБOï]

@davidesalvetti hi
your class needs Q_OBJECT macro

[J.Hilk]

@davidesalvetti in addition to what @LeLev said, your constructor is incomplete, you have to properly initialize the base class (QObject in this case)

[GrecKo]

@J.Hilk eh, not really. It's just that there won't be any QObject parent passed to the QObject constructor.

[J.Hilk]

@GrecKo well have to may be to strong of a wording, but one wouldn't want for bad habits to fester, right ;-)