Modbus Master example

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 #include "settingsdialog.h"
 #include "ui_settingsdialog.h"

 SettingsDialog::SettingsDialog(QWidget *parent) :
     QDialog(parent),
     ui(new Ui::SettingsDialog)
 {
     ui->setupUi(this);

     ui->parityCombo->setCurrentIndex(1);
     ui->baudCombo->setCurrentText(QString::number(m_settings.baud));
     ui->dataBitsCombo->setCurrentText(QString::number(m_settings.dataBits));
     ui->stopBitsCombo->setCurrentText(QString::number(m_settings.stopBits));
     ui->timeoutSpinner->setValue(m_settings.responseTime);
     ui->retriesSpinner->setValue(m_settings.numberOfRetries);

     connect(ui->applyButton, &QPushButton::clicked, [this]() {
         m_settings.parity = ui->parityCombo->currentIndex();
         if (m_settings.parity > 0)
             m_settings.parity++;
         m_settings.baud = ui->baudCombo->currentText().toInt();
         m_settings.dataBits = ui->dataBitsCombo->currentText().toInt();
         m_settings.stopBits = ui->stopBitsCombo->currentText().toInt();
         m_settings.responseTime = ui->timeoutSpinner->value();
         m_settings.numberOfRetries = ui->retriesSpinner->value();

         hide();
     });
 }

 SettingsDialog::~SettingsDialog()
 {
     delete ui;
 }

 SettingsDialog::Settings SettingsDialog::settings() const
 {
     return m_settings;
 }