如何将QML信号与C插槽连接？

我在QML中遇到messageDialog信号问题.在我的messageDialog中,我有两个用于是和否的按钮.我想用信号连接每个按钮.
这是我的qml文件：

import QtQuick 2.2
import QtQuick.Dialogs 1.1

Item{
    messageDialog {
        signal qmlYesSig(String msg)
        signal qmlNoSig (String msg)
        title: "Send data?"
        icon: StandarDicon.Question
        text: "Do you want to save your data on the online platform?"
        detailedText: "Click Yes "
        standardButtons: StandardButton.Yes | StandardButton.No
        Component.onCompleted: visible = true
        onYes: qmlYesSig("From yes")
        onNo: qmlNoSig("From no")
    }
}

这是我的插槽：

class MyClass : public QObject
{
    Q_OBjeCT
public slots:
    void cppSlot(const QString &msg) {
        qDebug() << "Called the C++ slot with message:" << msg;
    }
};

以下是我在main中如何使用它：

QQuickView view(QUrl::fromLocalFile("window.qml"));
QObject *item = view.rootObject();
AddData myClass;
QObject::connect(item,SIGNAL(qmlSignal(QString)),&myClass,SLOT(cppSlot(QString)));

view.show();

它给了我错误：

我已经尝试了很多次但是我无法工作QML信号和C插槽.
此外,我从这里尝试了Qt doc的例子并给了我同样的错误.

有人可以告诉我如何为messageDialog连接QML信号和C插槽吗？

Item{
    messageDialog {
        signal qmlYesSig(String msg)
        signal qmlNoSig (String msg)

        [...]
    }
}

QObject *item = view.rootObject();
AddData myClass;
QObject::connect(item,SLOT(cppSlot(QString)));

Item{}

Item{
    signal qmlSignal(String msg)

    messageDialog {
        onYes: parent.qmlSignal("From yes")
        onNo: parent.qmlSignal("From no")
    }
}