#include "widget.h"
#include "ui_widget.h"
//widget.cpp
Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);

    //连接槽  ,触发对象和接收都是自己
    QObject::connect(this ,SIGNAL(mysignal()) ,this ,SLOT(myslot()));
    QObject::connect( this ,SIGNAL(mysignalparams(int)) ,this ,SLOT(myslotparams(int)) );
    emit mysignal();        //触发信号
    emit mysignalparams(999);   //触发带参数的信号
}

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

void Widget::myslot()     //槽函数
{
    std::cout << "myslot" << std::endl;
}

void Widget::myslotparams(int value)
{
    std::cout << "myslotparams ," << value << std::endl;
    qDebug() << "This is value = " << value;
}

//widget.h
#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <iostream>
#include <QDebug>

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();

signals:            //自定义信号
    void mysignal();
    void mysignalparams(int value);

public slots:       //自定义槽
    void myslot();
    void myslotparams(int value);

private:
    Ui::Widget *ui;
};
#endif // WIDGET_H

       执行结果

5.2、例2

        创建两个类，比如Sender和Receiver。Sender类将发出信号，而Receiver类将接收并处理这个信号。

// Sender.h  
#ifndef SENDER_H  
#define SENDER_H  
  
#include <QObject>  
  
class Sender : public QObject {  
    Q_OBJECT  
public:  
    explicit Sender(QObject *parent = nullptr);  
  
signals:      
    void mySignal();      //信号
  
public slots:  
    void emitSignal();  
};  
  
#endif // SENDER_H

// Sender.cpp  
#include "Sender.h"  
  
Sender::Sender(QObject *parent) : QObject(parent) {  
}  
  
void Sender::emitSignal() {  
    emit mySignal();          //发送信号
}

// Receiver.h  
#ifndef RECEIVER_H  
#define RECEIVER_H  
  
#include <QObject>  
#include <QDebug>  
  
class Receiver : public QObject {  
    Q_OBJECT  
public:  
    explicit Receiver(QObject *parent = nullptr);  
  
public slots:  
    void handleSignal();      //槽函数
};  
  
#endif // RECEIVER_H

// Receiver.cpp  
#include "Receiver.h"  
  
Receiver::Receiver(QObject *parent) : QObject(parent) {  
}  
  
void Receiver::handleSignal() {  
    qDebug() << "Signal received!";  //槽函数
}

// main.cpp  
#include <QCoreApplication>  
#include "Sender.h"  
#include "Receiver.h"  
  
int main(int argc, char *argv[]) {  
    QCoreApplication a(argc, argv);  
  
    Sender sender;  
    Receiver receiver;  
  
    //连接信号与槽
    QObject::connect(&sender, &Sender::mySignal, &receiver, &Receiver::handleSignal);  
  
    sender.emitSignal(); // 调用函数发送信号
  
    return a.exec();  
}

6、QDebug()

qDebug() << "This is a debug message";
int value = 10;
qDebug() << "The value is" << value;