qmlscene dummydata

[lqsa]

I have this qml:

main.qml

import QtQuick 2.4
import QtQuick.Controls 1.3
 
Item {
    property alias text: t.text
    anchors.fill: parent
    Text {
        id: t
    }
}

import QtQuick 2.4
import QtQuick.Controls 1.3

Item {
    property alias text: t.text
    anchors.fill: parent
    Text {
        id: t
    }
}

To copy to clipboard, switch view to plain text mode 

What must I put on the dummydata directory to show "Hello" on the text item?

[anda_skoa]

How do you use your tyoe?
I.e where to you set the "text" property?

Cheers,
_

[lqsa]

C++ code assigns the text property, but for desiging I need to assign it to view the results.

I put this simple sample only for simplicity, but imagine a complex design with some properties. It's difficult view the final result on qmlscene if these properties hasn't any value.

[anda_skoa]

What do you mean C++ assigns the property?

Aren't binding a C++ provided value to the property in the QML code that uses your element?

Cheers,
_

[lqsa]

The C++ code, loads the qml and assigns the property text with setProperty:

item->setProperty("text", text);

item->setProperty("text", text);

To copy to clipboard, switch view to plain text mode 

[anda_skoa]

And why on earth would you do that?

If you would properly use an exported object with properties, you would not only have a better setup, you could also use dummydata.

Cheers,
_

[lqsa]

Sorry, I can't understand you.

My question is only what must to put on dummydata to appears "Hello" on the Text item. What file must be created? t.qml? main.qml? and what contents? text: "Hello"?. I'll tried these, but doesn't work.

[anda_skoa]

dummydata is a way to replace externally referenced data, e.g. data exposed by C++ objects.
You don't use any externally referenced data, so there is nothing dummydata could replace.

If you insist on your strange approach of passing data from C++ to QML, you'll have to write a QML file that also sets the text property from outside.
Since your filename it not suitable for usage as an element, you'll have to use a Loader or JavaScript (Qt.createComponent and createObject).

Alternatively you could consider using the recommended C++ intergration approach with externally referenced data and using dummy data directly.

Cheers,
_

[lqsa]

Ok, Finally I understand it, thank you very much.

I'm using this code to show a message that is generated from C++. The actual approach is to call setProperty("text", text) like suggested on Interacting with QML Objects from C++

Reading your answer, you consider that isn't a good approach? what approach do you suggest?

[anda_skoa]

The generally recommended approach is to avoid making C++ depend on QML, but instead make QML depend on C++.

This way the QML side, especially if it is used for UI with QtQuick, can be changed without needing to also change the C++ code.
E.g. when UI requirements change or when designers are working on the QML side and cannot modify C++ code themselves.

That is, the C++ side provides data and functionality and the QtQuick side decides how and when to make use of that data and when to invoke C++ functionality.

The way to do that is to expose objects created on the C++ side to the QQmlEngine, provide data via properties on these objects and have slots and invokable methods available for the functionality (if necessary).

Aside from avoiding dependencies from C++ toward QML, this also allows to use the data in a declarative fashion, e.g. in QML property bindings.

So instead of getting an item from the QML object tree and hoping that is has a property of a given name, with a hopefully compatible type, the application code just sets one of more objects (instance of QObject derived classes) via setContextProperty() and lets the QML side decide where it wants to assign which value to which property.

See http://doc.qt.io/qt-5/qtqml-cppinteg...ttributes.html

qmlscene's dummydata mechanism can then be used to mimick or mock these exposed objects, simply by having a dummydata QML file with the same name that was used in the setContextProperty() call that exposed the actual object.

Cheers,
_

[lqsa]

Cool! I'll rewritten my code with this approach.

Thank you very much.
Cheers.