Qt:qmessagebox message box, custom signal and slot

One 、QMessageBox Message box

#include "widget.h"

#include <QApplication>
#include <QMessageBox>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
//    QMessageBox::information(&w," Tips "," Make nucleic acid ");
//    QMessageBox::StandardButton ret = QMessageBox::question(&w," Tips "," Have you made nucleic acid ");
//    if(ret == QMessageBox::Yes)
//    {
//       QMessageBox::information(&w," Tips "," That's great ");
//   }
//   else
//   {
//       QMessageBox::critical(&w," Tips "," Go and do it ");
//   }
//
//
 QMessageBox mb(QMessageBox::NoIcon," Tips "," Click ",QMessageBox::Yes|QMessageBox::No,&w);
//   QMessageBox mb;
//
//   mb.setWindowTitle(" Tips ");
//   mb.setText(" Click ");
//
   // mb.addButton(" Tips ",QMessageBox::AcceptRole);
   // mb.addButton(" error ",QMessageBox::Cancel);
    w.show();

    int ret = mb.exec();

    if(ret == QMessageBox::AcceptRole)
    {
        QMessageBox::information(&w," Tips "," That's great ");
    }
    else
    {
        QMessageBox::critical(&w," Tips "," Go and do it ");
    }

    return a.exec();
}

Two 、 Custom signals and slots

1. Parameters of removing slots

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

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

private slots:
    void on_pushButton_clicked();

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

#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);

    QObject::connect(ui->pushButton,&QPushButton::clicked,this,&Widget::MySlot);
}

Widget::~Widget()
{
    delete ui;
}
void Widget::MySlot()
{
    ui->label->setText(" Big xx");
}

2. Small examples

#include "student.h"

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

}
void Student::Treat()
{
    QMessageBox::information(nullptr," Tips "," Dinner ");
}

#include "teacher.h"

Teacher::Teacher(QObject *parent) : QObject(parent)
{

}
void Teacher::ClassOver()
{
    QMessageBox::information(nullptr," Tips "," i am hungry , Class is over ");
    emit Hungry();
}

#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    pTe = new Teacher;
    pSt = new Student;

    QObject::connect(ui->pushButton,&QPushButton::clicked,pTe,&Teacher::ClassOver);
    QObject::connect(pTe,&Teacher::Hungry,pSt,&Student::Treat);
}

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

Output ：