1.Teacher类下定义信号signals:

Student类下定义槽函数：

Teacher.h

#pragma once#include <QObject>class Teacher  : public QObject
{Q_OBJECTpublic:Teacher(QObject *parent);~Teacher();
signals:void Ask();  //老师向学生提问void Ask(QString str);
};

Teacher.cpp

#include "Teacher.h"Teacher::Teacher(QObject *parent): QObject(parent)
{}Teacher::~Teacher()
{}

Student.h

#pragma once#include <QObject>#include <QDebug>
#include <QMessageBox>class Student  : public QObject
{Q_OBJECTpublic slots:void Answer();void Answer(QString str);
public:Student(QObject *parent);~Student();
};

Student.cpp

#include "Student.h"Student::Student(QObject *parent): QObject(parent)
{}Student::~Student()
{}void Student::Answer()
{QMessageBox::information(NULL, "Message", "student answer the question",QMessageBox::Ok|QMessageBox::Cancel);}void Student::Answer(QString str)
{QMessageBox::information(NULL, "Message", str+": Answer Is OK", QMessageBox::Ok | QMessageBox::Cancel);}

QSingalSlot.h

#include "ui_QSingalSlot.h"#include "Teacher.h"
#include "Student.h"class QSingalSlot : public QWidget
{Q_OBJECTpublic:QSingalSlot(QWidget *parent = nullptr);~QSingalSlot();Teacher* tech;Student* stud;
public slots:void AskQuestion();private:Ui::QSingalSlotClass ui;
};

QSingalSlot.cpp

#include "QSingalSlot.h"QSingalSlot::QSingalSlot(QWidget *parent): QWidget(parent)
{ui.setupUi(this);this->tech=new Teacher(nullptr);this->stud=new Student(nullptr);//函数指针void (Teacher:: * teachSignal)(QString) = &Teacher::Ask;void (Student:: * studentSlot)(QString) = &Student::Answer;// connect(tech, SIGNAL(Teacher::Ask()), stud, SLOT(Student::Answer()));  //写法调用不了// connect(tech, &Teacher::Ask, stud, &Student::Answer);connect(tech, teachSignal, stud, studentSlot);connect(ui.pushButton_Ask, SIGNAL(clicked()), this, SLOT(AskQuestion()));
}QSingalSlot::~QSingalSlot()
{}void QSingalSlot::AskQuestion()
{//emit tech->Ask();emit tech->Ask("yes or ok");
}