Passing Array from C++ to QML?

[raven-worx]

@MAthias_Va
you cannot pass an array directly to QML, but a QVariantList (see this)

[Bhushan_Sure]

@MAthias_Va you can access array element which is in C++ from qml, just call the function from qml and pass the parameter of "index". The function which is in C++, make that return type as "int or float" according to your requirement, by which you can get values in qml from C++ for that you don't need to pass array to qml

[MAthias_Va]

Can anyone provide a simple Example? I couldn't understand the provided doc?

[ODБOï]

hi
@MAthias_Va

have a class with Q_PROPERTY QVariantList

...
Q_PROPERTY(QVariantList arr READ getarr WRITE setarr)
public:
    const QVariantList & getarr() const { return m_arr; }
    void setarr(const QVariantList & v) { m_arr = v; }
private : 
   QVariantList  m_arr;
...

//fill the m_arr in ctor for example
...
 m_arr<<"1111"<<1111;
...

set an instance of that class as contextProperty so it can be reached from QML

  ThatClass bk;
  engine.rootContext()->setContextProperty("backend",&bk);

then use it

    property variant varList 
    Component.onCompleted : varList=backend.getarr
    onVarListChanged: {

        for (var i in varList){
            console.log(i)
        }
    }

[GrecKo]

Exposing a QList<int> as a property kind of works.
It's not directly usable as a model though, but since 5.12 you can easily make it work by doing : model: Array.from(myIntList)

You can also modify it by doing myIntList[index] = 42 or myIntList.push(51) (look at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array for reference)

[MAthias_Va]

Thx @LeLev, this was really helpfull, Now I am enjoying editing my array in QML :)

[ODБOï]

@MAthias_Va Nice happy coding !

[joaogatao]

@LeLev Thx for the snippet of code! I was looking for something like this.
It works fine for passing the entire array from QML to C++, but not for a single element in the list.

In my application I have a matrix of on/off buttons, so essentially several lists of booleans. I wonder if there is a more lightweight solution than passing the entire QVariantList each time a boolean flips value.

[ODБOï]

@joaogatao hi,
you can have a Q_Invokable method that takes the index you want to return

Q_INVOKABLE bool getButtonIndex(int i){
//err check 
 return arr.at(i);
}

note if you bind this to a value in QML, it will not refresh automatically when you change values in the c++ side
//ex:

CheckBox{
 checked : myObj.getButtonIndex(1) // will not be refreshed if **m_arr** changes c++ side
}

[joaogatao]

@LeLev and thx for fast response on an old topic :)
I just tried it and it does what I need

I'm pretty new to Qt. So much to learn.

Cheers