Passing QBitArrya to QML

[Damian7546]

Hi,
In my class I have code from this property:
Q_PROPERTY(QBitArray statusPrinter READ statusPrinter WRITE setStatusPrinter NOTIFY statusPrinterChanged)

In QML code I would like read this bits, I try in this way :

 Image {
        id: test
        anchors {
            left: parent.left
            leftMargin: 30
            top: keyInsert.bottom
            topMargin: 20
        }
        width: 70
        height: 70
        source: {
            if (systemController.statusPrinter(0) === 0)
                return "qrc:/UI/Assets/ok.png"
            if (systemController.statusPrinter(0) === 1)
                return "qrc:/UI/Assets/warrning.png"
        }
    }

but it doesn't work. What can be wrong ?

[JonB]

@Damian7546 said in Passing QBitArrya to QML:

return statusPrinter[bit];

Where do you get a C++ array named statusPrinter from? [Maybe I'm wrong, I don't do any QML :) ]. The error message actually tells you what is wrong; this is what you have:

const QBitArray &SystemController::statusPrinter() const

[Damian7546]

Probably I cannot pass an array directly to QML, so I need try in other way, like this:

class SystemController : public QObject
{
Q_PROPERTY(QList<StatusPrinter> statusPrinter READ statusPrinter WRITE setStatusPrinter NOTIFY statusPrinterChanged)
 .
 .
 .
 struct StatusPrinter
    {
        bool tempalert;
        bool printoutlost;
        bool paperjam;
        bool paperlow;
        bool outofpaper;
        bool poweron;
    };
};

And in QML:

var a = systemController.statusPrinter[0].tempalert

But still doesn't work, I have error:
TypeError: Cannot read property '0' of undefined

[freedbrt]

Just write help function which do it for you in the c++, for example

Q_INVOKABLE bool isBitSet(int bit) { return statusPrinter[bit]; }

[Damian7546]

I do not know how use it.... so in *.h I use in this way:

Q_PROPERTY(QBitArray statusPrinter READ statusPrinter WRITE setStatusPrinter NOTIFY statusPrinterChanged)

public:
Q_INVOKABLE bool isBitSet(int bit);

in definition in *.cpp

const QBitArray &SystemController::statusPrinter() const
{
    return m_statusPrinter;
}

void SystemController::setStatusPrinter(const QBitArray &newStatusPrinter)
{
    if (m_statusPrinter == newStatusPrinter)
        return;
    m_statusPrinter = newStatusPrinter;
    emit statusPrinterChanged();
}

bool SystemController::isBitSet(int bit)
{
    return statusPrinter[bit];

}

void SystemController::statusFromPrinter(QBitArray status)
{
    setStatusPrinter(status);
}

In this way I get error in return statusPrinter[bit]; line ::
systemcontroller.cpp:46:12: Reference to non-static member function must be called; did you mean to call it with no arguments? (fix available) insert '()'

[JonB]

@Damian7546 said in Passing QBitArrya to QML:

return statusPrinter[bit];

Where do you get a C++ array named statusPrinter from? [Maybe I'm wrong, I don't do any QML :) ]. The error message actually tells you what is wrong; this is what you have:

const QBitArray &SystemController::statusPrinter() const

[Damian7546]

@JonB

Can you explain me ? And how to pass this bits to QML?

[JonB]

@Damian7546
You have a "getter" method/function QBitArray &SystemController::statusPrinter(). You wrote statusPrinter[bit]. But you have to call the function, so statusPrinter() is necessary. The error message suggested

(fix available) insert '()'

To do it in one statement you will want

    return statusPrinter()[bit];
    // or
    return statusPrinter().at(bit);

[Damian7546]

Thank you very much.
Now I know how Q_INVOKABLE working.

The Q_INVOKABLE macro allows calling the function directly from QML, but I need
auto update bits value in QML when they change

In the public slots statusFromPrinter(QBitArray status) I pass 3 bits :

const QBitArray &SystemController::statusPrinter() const
{
    return m_statusPrinter;
}
void SystemController::setStatusPrinter(const QBitArray &newStatusPrinter)
{
    if (m_statusPrinter == newStatusPrinter)
        return;
    m_statusPrinter = newStatusPrinter;
    emit statusPrinterChanged();
}

bool SystemController::isBitSet(int bit)
{
    return statusPrinter()[bit];
}
void SystemController::statusFromPrinter(QBitArray status)
{
    qDebug()<< "Bits: " << status ;
    setStatusPrinter(status);
    
}

How update code in QML when bits on change

source: {
            if (systemController.isBitSet(1) === true)
                return "qrc:/UI/Assets/ok.png"
            if (systemController.isBitSet(1) === false)
                return "qrc:/UI/Assets/warrning.png"
        }

@JonB Can you help me ?

[JonB]

@Damian7546
No, because I said I know nothing about QML. "How update code in QML when bits on change": if you mean the bits change externally and you want something to update in QML when they do, I would guess you need to emit a signal when the bits get changed so that QML knows?

[Damian7546]

@JonB
Calling setStatusPrinter(status) I emited signal statusPrinterChanged() , so in QML I should read statusPrinter but it doesn't work- I can't read array in QML in this way systemController.statusPrinter()........

[Damian7546]

So, instead of using only one Q_PROPERTY(QBitArray status READ status WRITE setStatus NOTIFY statusChanged) a need use several Q_PROPERTY(bool statusX READ statusX WRITE setStatusX NOTIFY statusXChanged) to send my status to QML.
It not look optimally