Text {
    id: testData
    onTaskClicked:{
        testData.text = task.name
    }
}

ctxt->setContextProperty(QLatin1Literal("holiday"), m_model);
ctxt->setContextProperty(QLatin1Literal("bgcolor"), color);

view->setResizeMode(QQuickView::SizeRootObjectToView);

auto mainPath = QStandardPaths::locate(QStandardPaths::DataLocation,
                                           QLatin1Literal("taskview.qml"));

view->setSource(QUrl::fromLocalFile(mainPath));

ctxt->setContextProperty(QLatin1Literal("viewer"), m_view);

Q_SIGNALS:
    void taskClicked(HolidayTask* task);

auto root = view->rootObject();
auto myElement = root->findChild<QObject*>(QLatin1Literal("testData");

connect(m_view, SIGNAL(taskClicked(HolidayTask* task), myElement,
        SLOT(taskClicked(HolidayTask* task);

QML Connections: Cannot assign to non-existent property "onTaskClicked"

auto root = quickView->rootObject();
auto myElement = root->findChild<QObject*>(QLatin1Literal("testData"));

connect(m_view, SIGNAL(taskClicked(HolidayTask*)),
        myElement, SIGNAL(taskClicked(HolidayTask* task)));

Text {
    id: testData
    objectName: "testData"
    signal taskClicked(HolidayTask task)
    onTaskClicked: {
        testData.text = task.name
        console.log("CLICk!")
    }
}

QObject::connect: No such signal QQuickText_QML_0::taskClicked(HolidayTask* task) in /home/lb/Coding/cpp/holiday-planner/src/mainwindow.cpp:178
QObject::connect:  (receiver name: 'testData')

qmlRegisterType<HolidayTask>("HolidayPlanner", 1, 0, "HolidayTask");

import QtQuick 2.0
 import QtQml 2.2

import HolidayPlanner 1.0

Rectangle {
    id: container
    objectName: "container"
    color: bgcolor


   Text {
        id: testData
        objectName: "testData"
        signal taskClicked(HolidayTask task)
        onTaskClicked: {
            testData.text = task.name
            console.log("CLICK")
        }
   }

}

connect(m_view, SIGNAL(taskClicked(HolidayPlanner::HolidayTask*)),
        myElement, SIGNAL(taskClicked(HolidayPlanner::HolidayTask*)));

Text {
    id: testData
    objectName: "testData"
    // ^^^^^^^^^^^^^^^^^^^
    signal taskClicked (HolidayTask task)
    // ^^^^^^^^^^^^^^^^^^^
    onTaskClicked:{
        testData.text = task.name
    }
}

connect(m_view, SIGNAL(taskClicked(HolidayTask* task), myElement, SIGNAL(taskClicked(HolidayTask* task)));

view->rootContext()->setContextProperty("testData",this);
 QObject::connect(this,SIGNAL(taskClicked(HolidayTask* task)),(QObject *)view->rootObject(),SLOT(onTaskClicked(HolidayTask* task)));

objectName: "testData"

QML Connections: Cannot assign to non-existent property "onTaskClicked"

Text {
   id: testData
   objectName: "testData" // as Laszlo said

   function onTaskClicked( task ) {
       testData.text = task.name;
   }
}

Q_SIGNALS:
    void taskClicked(QVariant task);

emit taskClicked( QVariant::fromValue( task ) );

Text {
   id: testData
   objectName: "testData" // as Laszlo said

   signal taskClicked ( HolidayTask task )

   onTaskClicked: {
       testData.text = task.name;
   }
}

auto root = view->rootObject();
auto myElement = root->findChild<QObject*>(QLatin1Literal("testData");
connect(m_view, SIGNAL(taskClicked(HolidayTask*), myElement,
    SIGNAL(taskClicked(HolidayTask*));