declare property of pointer in qml

[themts]

Hey guys,

I have a view with several edit fields. Now I want to instantiate such view and pass a datamodel to it which will be used to fill the edit-fields etc.
How can I declare a property of pointer for my datamodel?

If I try this:

Item {
    id: thisIsMyCustomView
    width: 200
    height: 400

    property ClassNameOfModel dataModel
    //property ClassNameOfModel *dataModel  << This doesn't work

...
    TextField {
        text: dataModel.text1
        ...
    }

    TextField {
        text: dataModel.text2
        ...
    }

it would instanciate an object of ClassNameOfModel.

CU
mts

[p3c0]

@themts What is datamodel ?

[themts]

datamodel is a c-class.

[p3c0]

@themts So you can set datamodel as a contextProperty. More info here.

[themts]

ok, I think it's not clear what I want.

• I have a list with many objects in it (qList<ClassNameOfModel*>).
• I display the list with a combobox (list is assigned as model to combobox)
• I select one item in that combobox

until here, no problem.

Now I want to pass the selected item (ClassNameOfModel) to my common edit-component (qml-file) to display and edit some item-properties.
This common edit-component looks like this:

editComponent.qml:
Item {
    property ClassNameOfModel *dataModel << This doesn't work
    TextField {
        text: dataModel.text1
        ...
    }
    TextField {
        text: dataModel.text2
        ...
    }
    TextField {
        text: dataModel.text3
        ...
    }
   ...
}

How can I pass data to my custom-component?

[p3c0]

@themts Ok how do you call or load editComponent.qml ?

[themts]

???

editComponent {
id: edit1
}

My idea was to use onCurrentIndexChanged to assign the selected model to my editComponent:

    configComboBox.onCurrentIndexChanged: {
        edit.dataModel: configComboBox.model[configComboBox.currentIndex]
    }

[p3c0]

@themts AFAIK you can do this

property ClassNameOfModel dataModel

Have done something similar but with Rectangle.
What error do you get if you do it ?

[themts]

This declaration would create an instance of ClassNameOfModel.

[p3c0]

@themts I guess no. You can check it by printing dataModel. It should be null.

[themts]

@themts:
It doesn't work.
I register my dataModelClass like this:
qmlRegisterUncreatableType<ClassNameOfModel>("com.test.application", 1, 0, "ClassNameOfModel", "no no no");
As soon as I start my application I see the output:

...
qrc:/ConfigEdit.qml:3 Type ConfigEditEditForm unavailable
qrc:/ConfigEditEditForm.ui.qml:6 no no no

[p3c0]

@themts Can you post the complete compilable example ? Getting confused now O.o

[Buttink]

@themts This is a known problem with registering an uncreateable type. Its because QML is declarative. See this ticket https://bugreports.qt.io/browse/QTBUG-36752?jql=text ~ "Uncreatable C%2B%2B type can't be used for QML property types" . You have to just do QmlRegisterType<>. If you read the docs for qmlRegisterUncreatableType it says "This is useful where the type is only intended for providing attached properties or enum values.".

[themts]

@Buttink:
I already tried qmlRegisterType<ClassNameOfModel>() but then I get the message:
ClassNameOfModel is not a type

A workaround for me was now to declare a generic property var.
This way I have no code-completition but it works. Of course I would prefer a typesafe way.

I think it only works if I register the class as a creatable object, but then I have to implement a copyconstructor etc.

[Buttink]

@themts Hmmm that sounds really odd, but without the code, I don't know why it would output that error. I will say that you do not need a copy constructor. You could make a new qml type from

class Thing : public QObject
{
    Q_OBJECT
public:
    explicit Thing(QObject* parent = nullptr);
    virtual ~Thing();
};