如何在课堂上使用Qt信号和插槽？

问：

我用qt设计器创建了一个QtGuiApplication，并在其上添加了一个简单的类。尽管这个类继承自 QObject 类并且在私有部分Q_OBJECT宏，但代码没有运行，我遇到了这个错误：

LNK2001未解析的外部符号“public：虚拟结构 QMetaObject const * __cdecl Sender：：metaObject（void）const ” （？metaObject@Sender@@UEBAPEBUQMetaObject@@XZ）QtGui应用程序1

类头：

#ifndef SENDER_H
#define SENDER_H

#include <QObject>

class Sender : public QObject
{
    Q_OBJECT
public:
    explicit Sender(QObject *parent = 0);
    void fireSignal();

signals:
    void foo(const QString& arg);
};

#endif // SENDER_H

CPP类：

#include "Sender.h"

Sender::Sender(QObject *parent) :
    QObject(parent)
{
}


void Sender::fireSignal()
{
    emit foo("aa");
}

GUI 标头：

#pragma once
#include <QtWidgets/QMainWindow>
#include "ui_QtGuiApplication1.h"

class QtGuiApplication1 : public QMainWindow
{
    Q_OBJECT
public:
    QtGuiApplication1(QWidget *parent = Q_NULLPTR);
private:
    Ui::QtGuiApplication1Class ui;
};

图形用户界面 cpp：

#include "QtGuiApplication1.h"
#include <QPainter>

QtGuiApplication1::QtGuiApplication1(QWidget *parent)
    : QMainWindow(parent)
{
    ui.setupUi(this);
}

当我评论Q_OBJECT宏时，它起作用了。 我在哪里犯错误？谢谢。emit foo("aa");

已编辑：附加moc_Sender.cpp

/****************************************************************************
** Meta object code from reading C++ file 'Sender.h'
**
** Created by: The Qt Meta Object Compiler version 67 (Qt 5.11.1)
**
** WARNING! All changes made in this file will be lost!
*****************************************************************************/

#include "../../Sender.h"
#include <QtCore/qbytearray.h>
#include <QtCore/qmetatype.h>
#if !defined(Q_MOC_OUTPUT_REVISION)
#error "The header file 'Sender.h' doesn't include <QObject>."
#elif Q_MOC_OUTPUT_REVISION != 67
#error "This file was generated using the moc from 5.11.1. It"
#error "cannot be used with the include files from this version of Qt."
#error "(The moc has changed too much.)"
#endif

QT_BEGIN_MOC_NAMESPACE
QT_WARNING_PUSH
QT_WARNING_DISABLE_DEPRECATED
struct qt_meta_stringdata_Sender_t {
    QByteArrayData data[4];
    char stringdata0[16];
};
#define QT_MOC_LITERAL(idx, ofs, len) \
    Q_STATIC_BYTE_ARRAY_DATA_HEADER_INITIALIZER_WITH_OFFSET(len, \
    qptrdiff(offsetof(qt_meta_stringdata_Sender_t, stringdata0) + ofs \
        - idx * sizeof(QByteArrayData)) \
    )
static const qt_meta_stringdata_Sender_t qt_meta_stringdata_Sender = {
    {
QT_MOC_LITERAL(0, 0, 6), // "Sender"
QT_MOC_LITERAL(1, 7, 3), // "foo"
QT_MOC_LITERAL(2, 11, 0), // ""
QT_MOC_LITERAL(3, 12, 3) // "arg"

    },
    "Sender\0foo\0\0arg"
};
#undef QT_MOC_LITERAL

static const uint qt_meta_data_Sender[] = {

 // content:
       7,       // revision
       0,       // classname
       0,    0, // classinfo
       1,   14, // methods
       0,    0, // properties
       0,    0, // enums/sets
       0,    0, // constructors
       0,       // flags
       1,       // signalCount

 // signals: name, argc, parameters, tag, flags
       1,    1,   19,    2, 0x06 /* Public */,

 // signals: parameters
    QMetaType::Void, QMetaType::QString,    3,

       0        // eod
};

void Sender::qt_static_metacall(QObject *_o, QMetaObject::Call _c, int _id, void **_a)
{
    if (_c == QMetaObject::InvokeMetaMethod) {
        Sender *_t = static_cast<Sender *>(_o);
        Q_UNUSED(_t)
        switch (_id) {
        case 0: _t->foo((*reinterpret_cast< const QString(*)>(_a[1]))); break;
        default: ;
        }
    } else if (_c == QMetaObject::IndexOfMethod) {
        int *result = reinterpret_cast<int *>(_a[0]);
        {
            using _t = void (Sender::*)(const QString & );
            if (*reinterpret_cast<_t *>(_a[1]) == static_cast<_t>(&Sender::foo)) {
                *result = 0;
                return;
            }
        }
    }
}

QT_INIT_METAOBJECT const QMetaObject Sender::staticMetaObject = {
    { &QObject::staticMetaObject, qt_meta_stringdata_Sender.data,
      qt_meta_data_Sender,  qt_static_metacall, nullptr, nullptr}
};


const QMetaObject *Sender::metaObject() const
{
    return QObject::d_ptr->metaObject ? QObject::d_ptr->dynamicMetaObject() : &staticMetaObject;
}

void *Sender::qt_metacast(const char *_clname)
{
    if (!_clname) return nullptr;
    if (!strcmp(_clname, qt_meta_stringdata_Sender.stringdata0))
        return static_cast<void*>(this);
    return QObject::qt_metacast(_clname);
}

int Sender::qt_metacall(QMetaObject::Call _c, int _id, void **_a)
{
    _id = QObject::qt_metacall(_c, _id, _a);
    if (_id < 0)
        return _id;
    if (_c == QMetaObject::InvokeMetaMethod) {
        if (_id < 1)
            qt_static_metacall(this, _c, _id, _a);
        _id -= 1;
    } else if (_c == QMetaObject::RegisterMethodArgumentMetaType) {
        if (_id < 1)
            *reinterpret_cast<int*>(_a[0]) = -1;
        _id -= 1;
    }
    return _id;
}

// SIGNAL 0
void Sender::foo(const QString & _t1)
{
    void *_a[] = { nullptr, const_cast<void*>(reinterpret_cast<const void*>(&_t1)) };
    QMetaObject::activate(this, &staticMetaObject, 0, _a);
}
QT_WARNING_POP
QT_END_MOC_NAMESPACE