Struggle with struct, const QVector and register to QML

Krulle

Hello Guys,

I am currently trying to write an application for the Raspberry Pi.
I have compiled Qt version 5.15 and am using the latest QtCreator.

I'm struggling about an error during compilation:
Compilation error

I have a class "Core", which is registered in main.cpp as

    // init core-Application
    Core core;
    engine.rootContext()->setContextProperty("CoreApp", &core);

core.h

using namespace Gpio;

class Core : public QObject
{
    Q_OBJECT

    Q_PROPERTY(GpioBase gpioBase READ gpioBase)

public:
    explicit Core(QObject *parent = nullptr);

    const GpioBase &gpioBase() const;

private:
    GpioBase m_gpioBase;
}

I think the problem is here in class GpioBase (gpiobase.h):

namespace Gpio {

class GpioBase : public QObject
{
    Q_OBJECT

    Q_PROPERTY(QStringList gpioNameList READ gpioNameList)

public:
    explicit GpioBase(QObject *parent = nullptr);

    const QStringList &gpioNameList();

signals:

private:
    typedef enum gpioFunc {
        VCC = -1,
        IO,
        ALT
    } gpioFunc;

    struct gpio {
        int physical;
        int wPi;
        gpioFunc mode;
        QString altFunctionName;
        QString name;
    };

    const QVector<gpio> m_gpioList { // name (GPIOx), wPi
        gpio {1, -1, VCC, "", "3.3V"},
        gpio {2, -1, VCC, "", "5V"},
        gpio {3, 8, ALT, "SDA1", "GPIO 8"},
        gpio {4, -1, VCC, "", "5V"},
        gpio {5, 9, ALT, "SCL1", "GPIO 9"},
        gpio {6, -1, VCC, "", "0V"},
        gpio {7, 7, IO, "", "GPIO 7"},
        gpio {8, 15, ALT, "TxD", "GPIO 15"},
        gpio {9, -1, VCC, "", "0V"},
        gpio {10, 16, ALT, "RxD", "GPIO 16"},
        gpio {11, 0, IO, "", "GPIO 0"},
        gpio {12, 1, IO, "", "GPIO 1"},
        gpio {13, 2, IO, "", "GPIO 2"},
        gpio {14, -1, VCC, "", "0V"},
        gpio {15, 3, IO, "", "GPIO 3"},
        gpio {16, 4, IO, "", "GPIO 4"},
        gpio {17, -1, VCC, "", "3.3V"},
        gpio {18, 5, IO, "", "GPIO 5"},
        gpio {19, 12, ALT, "MOSI", "GPIO 12"},
        gpio {20, -1, VCC, "", "0V"},
        gpio {21, 13, ALT, "MISO", "GPIO 13"},
        gpio {22, 6, VCC, "", "GPIO"},
        gpio {23, 14, ALT, "SCLK", "GPIO 14"},
        gpio {24, 11, ALT, "CE0", "GPIO 10"},
        gpio {25, -1, VCC, "", "0V"},
        gpio {26, 11, ALT, "CE1", "GPIO 11"},
        gpio {27, 30, ALT, "SDA0", "GPIO 30"},
        gpio {28, 31, ALT, "SCL0", "GPIO 31"},
        gpio {29, 21, IO, "", "GPIO 21"},
        gpio {30, -1, VCC, "", "0V"},
        gpio {31, 22, IO, "", "GPIO 22"},
        gpio {32, 26, IO, "", "GPIO 26"},
        gpio {33, 23, IO, "", "GPIO 23"},
        gpio {34, -1, VCC, "", ""},
        gpio {35, 24, IO, "", "GPIO 24"},
        gpio {36, 27, IO, "", "GPIO 27"},
        gpio {37, 25, IO, "", "GPIO 25"},
        gpio {38, 28, IO, "", "GPIO 28"},
        gpio {39, -1, VCC, "", "0V"},
        gpio {40, 29, IO, "", "GPIO 29"}
    };

    QStringList m_gpioNameList;
};

}

gpiobase.cpp

using namespace Gpio;

GpioBase::GpioBase(QObject *parent) : QObject(parent)
{
    wiringPiSetup();

    // init list for gpio comboModel
    for(auto elem : m_gpioList) {
        if(elem.mode != VCC)
            m_gpioNameList.append(elem.mode == ALT ? QString("%1/%2").arg(elem.altFunctionName).arg(elem.name) : elem.name);
    }
}

const QStringList &GpioBase::gpioNameList()
{
    qDebug() << Q_FUNC_INFO;
    return m_gpioNameList;
}

Can you tell me what I'm doing wrong or which structure is not supported by Qt?

Thanks a lot!

Krulle

Okay, i've found a solution.
If change the parameter "gpiobase" to a pointer, it works.
But i don't know why.
Can anyone explain?

core.h

using namespace Gpio;

class Core : public QObject
{
    Q_OBJECT

    Q_PROPERTY(QPointer<GpioBase> gpioBase READ gpioBase CONSTANT)

public:
    explicit Core(QObject *parent = nullptr);
    ~Core() override;

    QPointer<GpioBase> gpioBase() const;

private:
    QPointer<GpioBase> m_gpioBase;


};

Christian Ehrlicher

@Krulle said in Struggle with struct, const QVector and register to QML:

Can anyone explain?

You get the error because QObject's are not copyable. When you use a pointer nothing gets copied since its... a pointer.