Access model owned by class in QML

Obi-Wan

Hi!

I've seen several topics on similar problems, but I still haven't been able to solve it, so I'm making a new thread.

I have a class, ModelManager, that owns an instance of MyListModel, inheriting from QAbstractListModel. The ModelManager is the .cpp backend that is exposed to QML through a call to setContextProperty in main.cpp.

I would like to access myListModel in QML and use it as a model for a Repeater.

My idea was to have the ModelManager own an instance of myListModel and have a Q_INVOKABLE getter in ModelManager.

In ModelManager I have:

class ModelManager : QObject
{
Q_OBJECT
public:
ModelManager(QObject* parent = 0);
Q_INVOKABLE MyListModel* myListModel() {return &myListModel_;}
private:
MyListModel myListModel_;
}

And in the Repeater I want to write:

Repeater
{
model: manager.myListModel()
...
}

I can't get it working however. I've read several posts about out it here on the forum. Some mention qmlRegisterType, which I've tried calling in my main.cpp with no luck.

qmlRegisterType<MyListModel>("ListModel",1,0, "listModel");

and then importing it with:

import ListModel 1.0

But no matter what I try, I always get the error:

Unkown return type: MyListModel*

I've also tried returing QObject* in myListModel(). This runs, but I get a very nasty error and crash, I'm assuming when the Repeater actually tries to access the model.

Any ideas about what I'm getting wrong?

literA2

@Obi-Wan you don't need to have a Q_INVOKABLE getter to expose your MyListModel into QML components instead use QQmlContext class, try it this way:

//main.cpp
QQmlContext *context = new QQmlContext(engine.rootContext());
context->setContextProperty("myListModel", &myListModel);

//qml file
Repeater
{
   model: myListModel
   ...
}

Obi-Wan

@literA2 Thanks!

This seems to work, as in the text turns blue if I write myListModel in QML, but I'm having a hard time confirming if it does!

myListModel currently is a list of doubles, I tought I could should these in a QML window by writing:

ListView
{
id: testView
width: 200
height: 200
x: 50
y: 50
model: myListModel

delegate: Text {
text: display // As this is the default role
}

Shouldn't this work?

literA2

@Obi-Wan in order to use the model properties in delegate, this is the syntax:

model.<propertyName>

Obi-Wan

@literA2 Thanks again, that does indeed work!

I'm not sure what I'm doing wrong, but I often have trouble figuring out these smaller details. I keep looking in the documentation, but I guess I keep looking in the wrong place.

In any case, my complete solution to the original problem is, as per @literA2's suggestion, to use setContextProperty in main.cpp. The model is still owned by the modelManager in my case, but I expose the model to QML in main.cpp by calling a getter.

main.cpp

ModelManager modelManager;

QQmlApplicationEngine engine;
engine.rootContext()->setContextProperty("myListModel", modelManager.myListModel());

...

myListModel() returns a pointer to the MyListModel of the ModelManager.

In my case, I can test that this works by having a ListView that displays the contents of the model like this. I'm using the default display role currently.

ListView
{
id: testView
width: 200
height: 200
x: 50
y: 50
model: myListModel

delegate: Text {
text: model.display
}

literA2

@Obi-Wan i think you don't need to exposed your modelManager, you can omit that line.

Obi-Wan

@literA2 said in Access model owned by class in QML:

@Obi-Wan i think you don't need to exposed your modelManager, you can omit that line.

You are absolutely right I think, it is only there because I'm using for something else. I'll remove it here for clarity.