Static struct member declaration

lukutis222

Hello. From what I understand, static members declared within class will share their value within different class objects. I would like to learn more about this and implement this myself. I have a class called settingswindow:

settingswindow.h:



#ifndef SETTINGSWINDOW_H
#define SETTINGSWINDOW_H

#include <QDialog>
#include <QSerialPort>


QT_BEGIN_NAMESPACE



namespace Ui {
class SettingsWindow;
}


QT_END_NAMESPACE

class SettingsWindow : public QDialog
{

    Q_OBJECT

public:



    Ui::SettingsWindow *m_ui = nullptr; //declared public so testool can reach it


    struct Settings {
        QString name;
        qint32 baudRate;
        QString stringBaudRate;
        QSerialPort::DataBits dataBits;
        QString stringDataBits;
        QSerialPort::Parity parity;
        QString stringParity;
        QSerialPort::StopBits stopBits;
        QString stringStopBits;
        QSerialPort::FlowControl flowControl;
        QString stringFlowControl;
        bool localEchoEnabled;
        bool log_to_file;
        bool hex_encode;
    };

    static Settings m_currentSettings;
    static Settings m_currentSettings2;

    explicit SettingsWindow(QWidget *parent = nullptr);
    ~SettingsWindow();

    Settings settings() const;
    Settings settings2() const;

private slots:
    void showPortInfo(int idx);
    void showPortInfo2(int idx);
    void apply();






    void on_serialPortInfoListBox_highlighted(int index);



private:

    void fillPortsParameters();
    void fillPortsParameters2();
    void fillPortsInfo2();
    void fillPortsInfo();
    void updateSettings();
    void updateSettings2();


    void rectangle_test();

private:

    //Ui::SettingsWindow *m_ui = nullptr; //declared public so testool can reach it


};

#endif // SETTINGSDIALOG_H

settingswindow.cpp:



#include "settingswindow.h"
#include "ui_settingswindow.h"
#include <QLineEdit>
#include <QSerialPortInfo>


static const char blankString[] = QT_TRANSLATE_NOOP("SettingsDialog", "N/A");



SettingsWindow::SettingsWindow(QWidget *parent) :
    QDialog(parent),
    m_ui(new Ui::SettingsWindow)

{




    //add the following line:



    //TestTool testtool_class;
    m_ui->setupUi(this);
//    ui->tabWidget->setStyleSheet("QTabWidget::pane { background-color: rgb(25, 33, 40); border:none}");
/*
    this->setStyleSheet( "QDialog{background-color: rgb(25, 33, 40);}");
    m_ui->descriptionLabel->setStyleSheet("QLabel { background-color: rgb(11, 33, 40); color : white; }");
    m_ui->baudRateLabel->setStyleSheet("QLabel { background-color: rgb(11, 33, 40); color : white; }");
    m_ui->flowControlLabel->setStyleSheet("QLabel { background-color: rgb(11, 33, 40); color : white; }");
    m_ui->locationLabel->setStyleSheet("QLabel { background-color: rgb(11, 33, 40); color : white;}");
    m_ui->dataBitsLabel->setStyleSheet("QLabel { background-color: rgb(11, 33, 40); color : white;}");
    m_ui->stopBitsLabel->setStyleSheet("QLabel { background-color: rgb(11, 33, 40); color : white;}");
    m_ui->manufacturerLabel->setStyleSheet("QLabel { background-color: rgb(11, 33, 40); color : white;}");
    m_ui->parityLabel->setStyleSheet("QLabel { background-color: rgb(11, 33, 40); color : white;}");
    m_ui->pidLabel->setStyleSheet("QLabel { background-color: rgb(11, 33, 40); color : white;}");
    m_ui->serialNumberLabel->setStyleSheet("QLabel { background-color: rgb(11, 33, 40); color : white;}");
    m_ui->vidLabel->setStyleSheet("QLabel { background-color: rgb(11, 33, 40); color : white;}");

    m_ui->localEchoCheckBox->setStyleSheet("QCheckBox { background-color: rgb(11, 33, 40); color : white;}");
    m_ui->log_to_file_checkbox->setStyleSheet("QCheckBox { background-color: rgb(11, 33, 40); color : white; }");
    m_ui->hex_encode_checkbox->setStyleSheet("QCheckBox { background-color: rgb(11, 33, 40); color : white; }");


    m_ui->selectBox->setStyleSheet("QGroupBox::title {color : white;}");
    m_ui->parametersBox->setStyleSheet("QGroupBox::title {color : white;}");
    m_ui->additionalOptionsGroupBox->setStyleSheet("QGroupBox::title {color : white;}");
    //ui->Console_read2->setStyleSheet("QTextEdit { background-color: rgb(11, 33, 40); color : white;  border: 1px solid white;}");


    m_ui->baudRateBox->setInsertPolicy(QComboBox::NoInsert);
    */

    connect(m_ui->applyButton, &QPushButton::clicked,
            this, &SettingsWindow::apply);

    connect(m_ui->serialPortInfoListBox, &QComboBox::currentIndexChanged,
            this, &SettingsWindow::showPortInfo);

    connect(m_ui->serialPortInfoListBox_2, &QComboBox::currentIndexChanged,
            this, &SettingsWindow::showPortInfo2);





    fillPortsParameters();
    fillPortsInfo();

    fillPortsParameters2();
    fillPortsInfo2();

    updateSettings();
    updateSettings2();

}

SettingsWindow::~SettingsWindow()
{
    delete m_ui;
}

SettingsWindow::Settings SettingsWindow::settings() const
{
    return m_currentSettings;
}


SettingsWindow::Settings SettingsWindow::settings2() const
{
    return m_currentSettings2;
}


void SettingsWindow::showPortInfo(int idx)
{
    if (idx == -1)
        return;

    const QStringList list = m_ui->serialPortInfoListBox->itemData(idx).toStringList();
    m_ui->descriptionLabel->setText(tr("Description: %1").arg(list.count() > 1 ? list.at(1) : tr(blankString)));
    m_ui->manufacturerLabel->setText(tr("Manufacturer: %1").arg(list.count() > 2 ? list.at(2) : tr(blankString)));
    m_ui->serialNumberLabel->setText(tr("Serial number: %1").arg(list.count() > 3 ? list.at(3) : tr(blankString)));
    m_ui->locationLabel->setText(tr("Location: %1").arg(list.count() > 4 ? list.at(4) : tr(blankString)));
    m_ui->vidLabel->setText(tr("Vendor Identifier: %1").arg(list.count() > 5 ? list.at(5) : tr(blankString)));
    m_ui->pidLabel->setText(tr("Product Identifier: %1").arg(list.count() > 6 ? list.at(6) : tr(blankString)));
}

void SettingsWindow::showPortInfo2(int idx)
{
    if (idx == -1)
        return;

    const QStringList list = m_ui->serialPortInfoListBox_2->itemData(idx).toStringList();
    m_ui->descriptionLabel_2->setText(tr("Description: %1").arg(list.count() > 1 ? list.at(1) : tr(blankString)));
    m_ui->manufacturerLabel_2->setText(tr("Manufacturer: %1").arg(list.count() > 2 ? list.at(2) : tr(blankString)));
    m_ui->serialNumberLabel_2->setText(tr("Serial number: %1").arg(list.count() > 3 ? list.at(3) : tr(blankString)));
    m_ui->locationLabel_2->setText(tr("Location: %1").arg(list.count() > 4 ? list.at(4) : tr(blankString)));
    m_ui->vidLabel_2->setText(tr("Vendor Identifier: %1").arg(list.count() > 5 ? list.at(5) : tr(blankString)));
    m_ui->pidLabel_2->setText(tr("Product Identifier: %1").arg(list.count() > 6 ? list.at(6) : tr(blankString)));
}

void SettingsWindow::apply()
{
    updateSettings();
    updateSettings2();
    hide();
}




void SettingsWindow::fillPortsParameters()
{
    m_ui->baudRateBox->addItem(QStringLiteral("9600"), QSerialPort::Baud9600);
    m_ui->baudRateBox->addItem(QStringLiteral("19200"), QSerialPort::Baud19200);
    m_ui->baudRateBox->addItem(QStringLiteral("38400"), QSerialPort::Baud38400);
    m_ui->baudRateBox->addItem(QStringLiteral("115200"), QSerialPort::Baud115200);
    m_ui->baudRateBox->addItem(tr("Custom"));

    m_ui->dataBitsBox->addItem(QStringLiteral("5"), QSerialPort::Data5);
    m_ui->dataBitsBox->addItem(QStringLiteral("6"), QSerialPort::Data6);
    m_ui->dataBitsBox->addItem(QStringLiteral("7"), QSerialPort::Data7);
    m_ui->dataBitsBox->addItem(QStringLiteral("8"), QSerialPort::Data8);
    m_ui->dataBitsBox->setCurrentIndex(3);

    m_ui->parityBox->addItem(tr("None"), QSerialPort::NoParity);
    m_ui->parityBox->addItem(tr("Even"), QSerialPort::EvenParity);
    m_ui->parityBox->addItem(tr("Odd"), QSerialPort::OddParity);
    m_ui->parityBox->addItem(tr("Mark"), QSerialPort::MarkParity);
    m_ui->parityBox->addItem(tr("Space"), QSerialPort::SpaceParity);

    m_ui->stopBitsBox->addItem(QStringLiteral("1"), QSerialPort::OneStop);
#ifdef Q_OS_WIN
    m_ui->stopBitsBox->addItem(tr("1.5"), QSerialPort::OneAndHalfStop);
#endif
    m_ui->stopBitsBox->addItem(QStringLiteral("2"), QSerialPort::TwoStop);

    m_ui->flowControlBox->addItem(tr("None"), QSerialPort::NoFlowControl);
    m_ui->flowControlBox->addItem(tr("RTS/CTS"), QSerialPort::HardwareControl);
    m_ui->flowControlBox->addItem(tr("XON/XOFF"), QSerialPort::SoftwareControl);
}




void SettingsWindow::fillPortsParameters2()
{
    m_ui->baudRateBox_2->addItem(QStringLiteral("9600"), QSerialPort::Baud9600);
    m_ui->baudRateBox_2->addItem(QStringLiteral("19200"), QSerialPort::Baud19200);
    m_ui->baudRateBox_2->addItem(QStringLiteral("38400"), QSerialPort::Baud38400);
    m_ui->baudRateBox_2->addItem(QStringLiteral("115200"), QSerialPort::Baud115200);
    m_ui->baudRateBox_2->addItem(tr("Custom"));

    m_ui->dataBitsBox_2->addItem(QStringLiteral("5"), QSerialPort::Data5);
    m_ui->dataBitsBox_2->addItem(QStringLiteral("6"), QSerialPort::Data6);
    m_ui->dataBitsBox_2->addItem(QStringLiteral("7"), QSerialPort::Data7);
    m_ui->dataBitsBox_2->addItem(QStringLiteral("8"), QSerialPort::Data8);
    m_ui->dataBitsBox_2->setCurrentIndex(3);

    m_ui->parityBox_2->addItem(tr("None"), QSerialPort::NoParity);
    m_ui->parityBox_2->addItem(tr("Even"), QSerialPort::EvenParity);
    m_ui->parityBox_2->addItem(tr("Odd"), QSerialPort::OddParity);
    m_ui->parityBox_2->addItem(tr("Mark"), QSerialPort::MarkParity);
    m_ui->parityBox_2->addItem(tr("Space"), QSerialPort::SpaceParity);

    m_ui->stopBitsBox_2->addItem(QStringLiteral("1"), QSerialPort::OneStop);
#ifdef Q_OS_WIN
    m_ui->stopBitsBox_2->addItem(tr("1.5"), QSerialPort::OneAndHalfStop);
#endif
    m_ui->stopBitsBox_2->addItem(QStringLiteral("2"), QSerialPort::TwoStop);

    m_ui->flowControlBox_2->addItem(tr("None"), QSerialPort::NoFlowControl);
    m_ui->flowControlBox_2->addItem(tr("RTS/CTS"), QSerialPort::HardwareControl);
    m_ui->flowControlBox_2->addItem(tr("XON/XOFF"), QSerialPort::SoftwareControl);
}


void SettingsWindow::fillPortsInfo()
{
    m_ui->serialPortInfoListBox->clear();
    QString description;
    QString manufacturer;
    QString serialNumber;
    const auto infos = QSerialPortInfo::availablePorts();
    for (const QSerialPortInfo &info : infos) {
        QStringList list;
        description = info.description();
        manufacturer = info.manufacturer();
        serialNumber = info.serialNumber();
        list << info.portName()
             << (!description.isEmpty() ? description : blankString)
             << (!manufacturer.isEmpty() ? manufacturer : blankString)
             << (!serialNumber.isEmpty() ? serialNumber : blankString)
             << info.systemLocation()
             << (info.vendorIdentifier() ? QString::number(info.vendorIdentifier(), 16) : blankString)
             << (info.productIdentifier() ? QString::number(info.productIdentifier(), 16) : blankString);

        m_ui->serialPortInfoListBox->addItem(list.first(), list);
    }

    m_ui->serialPortInfoListBox->addItem(tr("Custom"));
}



void SettingsWindow::fillPortsInfo2()
{
    m_ui->serialPortInfoListBox_2->clear();
    QString description;
    QString manufacturer;
    QString serialNumber;
    const auto infos = QSerialPortInfo::availablePorts();
    for (const QSerialPortInfo &info : infos) {
        QStringList list;
        description = info.description();
        manufacturer = info.manufacturer();
        serialNumber = info.serialNumber();
        list << info.portName()
             << (!description.isEmpty() ? description : blankString)
             << (!manufacturer.isEmpty() ? manufacturer : blankString)
             << (!serialNumber.isEmpty() ? serialNumber : blankString)
             << info.systemLocation()
             << (info.vendorIdentifier() ? QString::number(info.vendorIdentifier(), 16) : blankString)
             << (info.productIdentifier() ? QString::number(info.productIdentifier(), 16) : blankString);

        m_ui->serialPortInfoListBox_2->addItem(list.first(), list);
    }

    m_ui->serialPortInfoListBox_2->addItem(tr("Custom"));
}

void SettingsWindow::updateSettings()
{
    m_currentSettings.name = m_ui->serialPortInfoListBox->currentText();


    if (m_ui->baudRateBox->currentIndex() == 4) {
        m_currentSettings.baudRate = m_ui->baudRateBox->currentText().toInt();
    } else {
        m_currentSettings.baudRate = static_cast<QSerialPort::BaudRate>(
                    m_ui->baudRateBox->itemData(m_ui->baudRateBox->currentIndex()).toInt());
    }
    m_currentSettings.stringBaudRate = QString::number(m_currentSettings.baudRate);

    m_currentSettings.dataBits = static_cast<QSerialPort::DataBits>(
                m_ui->dataBitsBox->itemData(m_ui->dataBitsBox->currentIndex()).toInt());
    m_currentSettings.stringDataBits = m_ui->dataBitsBox->currentText();

    m_currentSettings.parity = static_cast<QSerialPort::Parity>(
                m_ui->parityBox->itemData(m_ui->parityBox->currentIndex()).toInt());
    m_currentSettings.stringParity = m_ui->parityBox->currentText();

    m_currentSettings.stopBits = static_cast<QSerialPort::StopBits>(
                m_ui->stopBitsBox->itemData(m_ui->stopBitsBox->currentIndex()).toInt());
    m_currentSettings.stringStopBits = m_ui->stopBitsBox->currentText();

    m_currentSettings.flowControl = static_cast<QSerialPort::FlowControl>(
                m_ui->flowControlBox->itemData(m_ui->flowControlBox->currentIndex()).toInt());
    m_currentSettings.stringFlowControl = m_ui->flowControlBox->currentText();

    m_currentSettings.localEchoEnabled = m_ui->localEchoCheckBox->isChecked();
    m_currentSettings.log_to_file = m_ui->log_to_file_checkbox->isChecked();
    m_currentSettings.hex_encode = m_ui->hex_encode_checkbox->isChecked();
}



void SettingsWindow::updateSettings2()
{
    m_currentSettings2.name = m_ui->serialPortInfoListBox_2->currentText();


    if (m_ui->baudRateBox_2->currentIndex() == 4) {
        m_currentSettings2.baudRate = m_ui->baudRateBox_2->currentText().toInt();
    } else {
        m_currentSettings2.baudRate = static_cast<QSerialPort::BaudRate>(
                    m_ui->baudRateBox_2->itemData(m_ui->baudRateBox_2->currentIndex()).toInt());
    }
    m_currentSettings2.stringBaudRate = QString::number(m_currentSettings2.baudRate);

    m_currentSettings2.dataBits = static_cast<QSerialPort::DataBits>(
                m_ui->dataBitsBox_2->itemData(m_ui->dataBitsBox_2->currentIndex()).toInt());
    m_currentSettings2.stringDataBits = m_ui->dataBitsBox_2->currentText();

    m_currentSettings2.parity = static_cast<QSerialPort::Parity>(
                m_ui->parityBox_2->itemData(m_ui->parityBox_2->currentIndex()).toInt());
    m_currentSettings2.stringParity = m_ui->parityBox_2->currentText();

    m_currentSettings2.stopBits = static_cast<QSerialPort::StopBits>(
                m_ui->stopBitsBox_2->itemData(m_ui->stopBitsBox_2->currentIndex()).toInt());
    m_currentSettings2.stringStopBits = m_ui->stopBitsBox_2->currentText();

    m_currentSettings2.flowControl = static_cast<QSerialPort::FlowControl>(
                m_ui->flowControlBox_2->itemData(m_ui->flowControlBox_2->currentIndex()).toInt());
    m_currentSettings2.stringFlowControl = m_ui->flowControlBox_2->currentText();

    m_currentSettings2.localEchoEnabled = m_ui->localEchoCheckBox_2->isChecked();
    m_currentSettings2.log_to_file = m_ui->log_to_file_checkbox_2->isChecked();
    m_currentSettings2.hex_encode = m_ui->hex_encode_checkbox_2->isChecked();
}









void SettingsWindow::on_serialPortInfoListBox_highlighted(int index)
{
    qDebug("highligted \n");
    //fillPortsInfo();
    //fillPortsInfo2();
}

As you can see from the settingswindow.h I have a struct called Settings:

    struct Settings {
        QString name;
        qint32 baudRate;
        QString stringBaudRate;
        QSerialPort::DataBits dataBits;
        QString stringDataBits;
        QSerialPort::Parity parity;
        QString stringParity;
        QSerialPort::StopBits stopBits;
        QString stringStopBits;
        QSerialPort::FlowControl flowControl;
        QString stringFlowControl;
        bool localEchoEnabled;
        bool log_to_file;
        bool hex_encode;
    };

I would like to understand more about how to create a static struct member. I tried to do:

    struct Settings {
        QString name;
        qint32 baudRate;
        QString stringBaudRate;
        QSerialPort::DataBits dataBits;
        QString stringDataBits;
        QSerialPort::Parity parity;
        QString stringParity;
        QSerialPort::StopBits stopBits;
        QString stringStopBits;
        QSerialPort::FlowControl flowControl;
        QString stringFlowControl;
        bool localEchoEnabled;
        bool log_to_file;
        bool hex_encode;
    };

    static Settings m_currentSettings;
    static Settings m_currentSettings2;

But I get the following error:

Could someone help me understand how to properly create static struct? Thanks in advance..

JonB

@lukutis222

    static Settings m_currentSettings;
    static Settings m_currentSettings2;

These are static global variables. The linker error indicates you have tried to access these (somewhere not shown?) via Settings::m_currentSettings. That would be a static member variable inside class Settings, which they are not.

What do you intend? You have two static Settings struct variables, that is not the problem. Do you wish these to be global scope variables or struct scope (really just namespace) variables? Or even static Settings variables inside some other class?

BTW. static is not always the best choice these days. It has various gotchas/restrictions. For example, yours would work, but if you decided to store any type derived from QObject inside it it would not. Often people use singleton objects for this.

lukutis222

@JonB
Thanks for response.

What I was trying to achieve is quite simple. I have class SettingsWindow and I create multiple objects:

SettingsWindow settings_obj1;
SettingsWindow settings_obj2;

I want both object to share same Settings struct (m_currentSettings and m_currentSettings2). If I change some Settings on one object, the other will change as well. I thought that static struct declaration would be good use for this.

JonB

@lukutis222
One possibility would be to create a single Settings instance and maintain a pointer to it in both SettingsWindow objects. Or the static you want. I believe the problem with that at present --- from the error message in the screenshot you posted --- is that your static Settings m_currentSettings defines a global object, outside of any class, while you have somewhere (elsewhere) in your code where you are trying to access it via Settings::m_currentSettings. That would be wrong and lead to the linker error you show. So do you have somewhere in code where you try to access that m_currentSettings object, what does that look like?

Christian Ehrlicher

If your last peice of code in your first post is from the class definition of SettingsWindow then you simply forgot to define your two member variables seomwhere since you only declared them in the header.
No idea why they need to be static though...

JonB

@lukutis222
Further to @Christian-Ehrlicher's response I now see that you seem to have:

class SettingsWindow : public QDialog
{
    ...
    static Settings m_currentSettings;
    static Settings m_currentSettings2;

In that case you will need to put into the .cpp file (somewhere at top-level scope, near the beginning but after #include "settingswindow.h"):

// in next two lines you may need `SettingsWindow::Settings` in place of plain `Settings`
static Settings SettingsWindow::m_currentSettings;
static Settings SettingsWindow::m_currentSettings2;

to define storage for these variables, and thereby get rid of the linker error.

mpergand

C++ is stupid enough that you have to declare static vars two times :)

Christian Ehrlicher

@mpergand said in Static struct member declaration:

C++ is stupid enough that you have to declare static vars two times :)

No, you have to declare it once and also define it once.
static pod members can be declared and defined in one place nowadays.