How can you: application logic in C++ and presentation in QML
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I just have some fun with QML and i love to use it to handle the UI, just UI!
For me, I will define a new QML Elements in C++ with some method that handle the main (and maybe taking some time) application logic and use it at event handle for the presentation elements, like this:
@Rectangle {
width: 360
height: 360
CustomCppDefinedElements {
id:foo
}
MouseArea {
anchors.fill: parent
onClicked: {
foo.DoIt();
}
}
}
@
But is there any better way?
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Who knows? Depends on what you need and what the circumstances are. What I usually do is either:
create a base C++ class inheriting from QQuickItem, add relevant methods and properties, register it and use in code to create children components
or create plain QObject classes in C++ and export methods with Q_INVOKABLE (or slots) and properties with Q_PROPERTY, and then register it with QQuickView's root object
I won't venture to say which is better - it depends on a concrete use case.
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In Qt5 with QtQuick2 there are more ways to expose C++ functionality to QML.
One particularly useful feature is the ability to register a QObject singleton type with the QML typesystem. You can call functions, bind to properties, etc, without having to explicitly instantiate an element or pass in a context property.See the "documentation":http://qt-project.org/doc/qt-5.0/qqmlengine.html#qmlRegisterSingletonType-2 for more information.
In short, yes - QML was designed with C++ integration in mind. You should implement heavy application logic in C++, and implement only your UI with QtQuick, in many cases.
Cheers,
Chris.
