檔案目錄

Teacher.h

#ifndef TEACHER_H
#define TEACHER_H

#include <QObject>

class Teacher : public QObject
{
    Q_OBJECT
public:
    explicit Teacher(QObject *parent = nullptr);

signals:
    void hungry(QString foodName);
    void hungry();


};

#endif // TEACHER_H

teacher.cpp

是訊號，不需要實現

student.h

#ifndef STUDENT_H
#define STUDENT_H

#include <QObject>
#include <QString>

class Student : public QObject
{
    Q_OBJECT
public:
    explicit Student(QObject *parent = nullptr);

signals:

public slots:
    // void 返回值型別，需要宣告和實現
    // 可以有引數，可以發生過載
    void say();
    void say(QString foodName);

};

#endif // STUDENT_H

 

student.cpp

#include "student.h"
#include <QDebug>


Student::Student(QObject *parent) : QObject(parent)
{

}

void Student::say()
{
    qDebug() << "Go Away!";

}

void Student::say(QString foodName)
{
    // QString先轉QByteArray，然後轉Char *
    qDebug() << "eat " << foodName.toUtf8().data();
}


 

mainwindows.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"



MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    this->setFixedSize(200, 100);

    QPushButton * buttonTech = new QPushButton;
    buttonTech->resize(80, 40);
    buttonTech->setText("class over");
    buttonTech->move(100, 10);
    buttonTech->setParent(this);

    this->tea = new Teacher(this);      // C++建立物件方式，h檔案宣告，C檔案指標new
    this->stu = new Student(this);

    // 函式過載，無參，不知道呼叫哪個地址的同名函式
    //connect(tea, &Teacher::hungry, stu, &Student::say);
    // 函式過載，有參,定義函式指標，指向類內函式的地址
    void(Teacher:: *teaSingal)(QString) = &Teacher::hungry;
    void(Student:: *stuSlot)(QString) = &Student::say;
    connect(tea, teaSingal, stu, stuSlot);    // 老師hungry訊號和學生say槽函式連線
    classIsOver();      // 發射老師hungry訊號

    // 按鈕觸發槽函式, 第三個引數，訊號的接受者是當前視窗類，並觸發視窗的槽函式
    // 按鈕觸發的訊號和這個視窗的classIsOver函式相連線，這個函式傳送emit hungry訊號
    connect(buttonTech, &QPushButton::clicked, this, &MainWindow::classIsOver);

    // 無引數的訊號和槽連線
    void(Teacher:: *teaSingalN)(void) = &Teacher::hungry;
    void(Student:: *stuSlotN)(void) = &Student::say;
    connect(tea, teaSingalN, stu, stuSlotN);
    classIsOver();      // 發射老師hungry訊號

    // 訊號和訊號的連線
    QPushButton * button = new QPushButton("signal", this);
    button->resize(50, 50);
    button->move(0, 0);
    connect(button, &QPushButton::clicked, stu, stuSlotN);

    // 訊號斷開, 上一行程式碼的connect，無效了
    disconnect(button, &QPushButton::clicked, stu, stuSlotN);
}

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

void MainWindow::classIsOver()
{
    emit tea->hungry("asd");
    emit tea->hungry();
}