Does really property var mdl: model copies the full model object in memory?



  • Hello guys,
    I faced with this issue that I have to pass forward some data from one QML component to another and thus I created property var mdl: model when model here is quite heavy object.
    Does QtQuick really copies this in memory or how does it works? and what is the difference with property alias?


  • Moderators

    Hi @Kofr,
    It is documented here. From the doc:

    Property aliases are properties which hold a reference to another property. Unlike an ordinary property definition, which allocates a new, unique storage space for the property, a property alias connects the newly declared property (called the aliasing property) as a direct reference to an existing property (the aliased property).

    So what I understand from it is that the first assignment (in your example) will copy into a new object while aliases holds the reference.



  • @p3c0 so model in example is a model defined in C++ and instantiated in QML.
    The question is
    Does QML makes copy of this object (2 data models in memory) or it keeps only reference.
    is it ducumented somewhere?



  • @Kofr Hi! If you want to be really sure (because you don't trust the docs or your code ^_^) then add something like qDebug() << "hello"; to the destructor of the model and see how often that's called.