Cannot assign QObject* to QQuickItem*

[Vinoth Rajendran4]

Hi All,

i am getting error at runtime (line number:29)

1     import QtQuick 2.0
2     import QtQuick.Window 2.2
3
4     Window {
5         id: rootW
6         visible: true
7
8         width : Screen.desktopAvailableWidth * 0.75
9         height: Screen.desktopAvailableHeight * 0.75
10
11         Rectangle {
12               id: parasite
13              parent: rootW
14              x: 10; y: 10; width: 100; height: 100
15               color: "blue"
16         }
17
18        Rectangle {
19           id: centreR
20            x: rootW.width * 0.25
21             y: rootW.height * 0.25
22             width: rootW.width * 0.5
23             height: rootW.height * 0.5
24            color: "green"
25
26              MouseArea {
27                    anchors.fill: centreR
28                    onClicked: {
29                          parasite.parent = rootW   // Error: Cannot assign QObject* to QQuickItem*
30                          centreR.destroy()
31                    }
32              }
33        }
34
35  }

I have two questions,
1. Is there any way we could do casting such as reinterpret_cast inside QML file, to overcome this error @ line number 29 ?
2. I wonder why error happens @ line 29, whereas we don't have any issue @ line number 13, doing the same operation ?

Thanks in advance!

[JKSH]

@Vinoth-Rajendran4 said in Cannot assign QObject* to QQuickItem*:

2. I wonder why error happens @ line 29, whereas we don't have any issue @ line number 13, doing the same operation ?

I'm not convinced that line #13 is meaningful. I think it's a silent error in Qt -- you should have received an error message.

Note: lines 13 and 29 are very different operations. Line #13 (:) sets up a property binding while line #29 (=) does an assignment. See https://doc.qt.io/qt-5/qtqml-syntax-propertybinding.html for details.

1. Is there any way we could do casting such as reinterpret_cast inside QML file, to overcome this error @ line number 29 ?

You cannot "overcome" the error.

Line #29 tries to call QQuickItem::setParentItem() (https://doc.qt.io/qt-5/qquickitem.html#parent-prop ). This function cannot accept a QQuickWindow*.

See also https://doc.qt.io/qt-5/qtquick-visualcanvas-visualparent.html to understand the different types of parents.

Can you tell us why you want to set the Rectangle's parent?

[Vinoth Rajendran4]

@JKSH , Thanks for the reply

Line #13 produce error, i din't see it before.
https://doc.qt.io/qt-5/qtqml-syntax-propertybinding.html , this link was useful.

I wrote this code to understand the difference between visual parent and object parent. I know it makes no sense. But since i found an error, i thought to get it clarified.

Thank You!