Qt:不能为MyClass类型的参数排队

我正试图通过这个信号传递我的类:

connect(this, SIGNAL(SIG_connectSerial(SerialSetting::Settings)), serial, SLOT(openConnection(SerialSetting::Settings)),Qt::QueuedConnection);

我想传递的类是这个类:

#ifndef SERIALSETTING_H
#define SERIALSETTING_H
#include <QWidget>
#include <QtSerialPort/QSerialPort>

namespace Ui {
class SerialSetting;
}   
class QIntValidator;
class SerialSetting : public QWidget
{
    Q_OBJECT
public:
    struct  Settings {
            QString portName;
            qint32 baudRate;
    };
    Settings settings();

public:
    explicit SerialSetting(QWidget *parent = 0);
    ~SerialSetting();
private slots:
    void apply();
    void on_btnApply_clicked();
private:
    void fillPortsParameters();
    void fillPortsInfo();
    void updateSettings();

private:
    Ui::SerialSetting *ui;
    Settings currentSettings;
    QIntValidator *intValidator;
};
#endif // SERIALSETTING_H
#include "serialsetting.h"
#include "ui_serialsetting.h"
#include <QtSerialPort/QSerialPortInfo>
#include <QIntValidator>
#include <QLineEdit>
QT_USE_NAMESPACE
static const char blankString[] = QT_TRANSLATE_NOOP("SettingsDialog", "N/A");
SerialSetting::SerialSetting(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::SerialSetting)
{
    ui->setupUi(this);
    intValidator = new QIntValidator(0, 4000000, this);
    //ui->cboBaudRate->setInsertPolicy(QComboBox::NoInsert);
    fillPortsParameters(); //call function to fill comboboxes
    connect(ui->btnApply, SIGNAL(clicked()),this, SLOT(apply()));
}
SerialSetting::~SerialSetting()
{
    delete ui;
}
void SerialSetting::fillPortsParameters()
{
//fill cboComport with all available comports
foreach(const QSerialPortInfo &info, QSerialPortInfo::availablePorts())
    {
    ui->cboComport->addItem(info.portName());
    }
}
void SerialSetting::apply()
{
    SerialSetting::currentSettings.portName = ui->cboComport->currentText();
    hide();
}
SerialSetting::Settings SerialSetting::settings()
{
    return SerialSetting::currentSettings;
}
void SerialSetting::on_btnApply_clicked()
{
}

编译器抛出以下异常:QObject::connect:无法对"SerialSetting::Settings"类型的参数进行排队(确保使用qRegisterMetaType()注册'SerialSetting::Settings'。)我尝试了qRegisterMetaType<SerialSetting>();，但这以以下错误结束:

static assertion failed: Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system
 #define Q_STATIC_ASSERT_X(Condition, Message) static_assert(bool(Condition), Message)

在类头的末尾添加Makro Q_DECLARE_METATYPE(Ui::SerialSetting)会抛出另一个错误:

invalid application of 'sizeof' to incomplete type 'Ui::SerialSetting'
         isLarge = (sizeof(T)>sizeof(void*)),