qmlRegisterType?

QQuickView view

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>

class Some : public QObject
{
    Q_OBJECT
public:
    Some(QObject *parent = nullptr)
        : QObject{parent}
    {}
signals:
    void done(QString msg);

public slots:
    Q_INVOKABLE void process() {
        emit done("finished");
    }
};

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

    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    qmlRegisterType<Some>();
    Some some;
    QQmlContext* context = engine.rootContext();
    context->setContextProperty("some", &some);
    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
        &app, [url](QObject *obj, const QUrl &objUrl) {
            if (!obj && url == objUrl)
                QCoreApplication::exit(-1);
        }, Qt::QueuedConnection);
    engine.load(url);

    return app.exec();
}

#include "main.moc"

import QtQuick 2.12
import QtQuick.Window 2.12
import QtQuick.Controls 2.12

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    Button {
        text: "click"
        onClicked: {
            some.process()
        }
    }

    Connections {
        target: some
        onDone: {
            console.log(msg)
        }
    }
}