Qt学习 第31节：信号和槽出现函数重载

https://doc.qt.io/qt-5/signalsandslots-syntaxes.html#https://doc.qt.io/qt-5/signalsandslots-syntaxes.html#

Selecting Overloaded Signals and Slots

With the string-based syntax, parameter types are explicitly specified. As a result, the desired instance of an overloaded signal or slot is unambiguous.

In contrast, with the functor-based syntax, an overloaded signal or slot must be casted to tell the compiler which instance to use.

For example, QLCDNumber has three versions of the display() slot:

1. QLCDNumber::display(int)
2. QLCDNumber::display(double)
3. QLCDNumber::display(QString)

To connect the int version to QSlider::valueChanged(), the two syntaxes are:

    auto slider = new QSlider(this);
    auto lcd = new QLCDNumber(this);

    // String-based syntax
    connect(slider, SIGNAL(valueChanged(int)),lcd, SLOT(display(int)));

    // Functor-based syntax, first alternative
    connect(slider, &QSlider::valueChanged,lcd, static_cast(&QLCDNumber::display));

    // Functor-based syntax, second alternative
    void (QLCDNumber::*mySlot)(int) = &QLCDNumber::display;
    connect(slider, &QSlider::valueChanged,lcd, mySlot);

    // Functor-based syntax, third alternative
    connect(slider, &QSlider::valueChanged,lcd, QOverload::of(&QLCDNumber::display));

    // Functor-based syntax, fourth alternative (requires C++14)
    connect(slider, &QSlider::valueChanged,lcd, qOverload(&QLCDNumber::display));

 See also qOverload().

Widgets and Dialogs with Auto-Connect

Qt学习 第4节：QMetaObject::connectSlotsByName(this)信号槽自动连接_人类工程师的博客-CSDN博客#include#include#include#includeint main(int argc,char* argv[]){ QApplication app(argc,argv); QWidget* window = new QWidget; window->setWindowTitle("Enter Your.https://blog.csdn.net/qq_50832904/article/details/121844898

Using a Designer UI File in Your Application | Qt 4.8https://doc.qt.io/archives/qt-4.8/designer-using-a-ui-file.html#automatic-connections

Student.h

#ifndef STUDENT_H
#define STUDENT_H

#include 

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

signals:
public slots:
    void treat();
    void treat(QString food);
};

#endif // STUDENT_H

    Student.cpp

#include "Student.h"
#include 
Student::Student(QObject *parent) : QObject(parent)
{

}

void Student::treat()
{
    qDebug()<<"请老师吃饭"<

    Teacher.h

#ifndef TEACHER_H
#define TEACHER_H

#include 

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

signals:
    void hungry();
    void hungry(QString food);
};

#endif // TEACHER_H

    Teacher.cpp

#include "Teacher.h"

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

}

    Widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include 
#include "Teacher.h"
#include "Student.h"

class Widget : public QWidget
{
    Q_OBJECT

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

private:
    Teacher* teacherZhang;
    Student* studentWang;
};
#endif // WIDGET_H

Widget.cpp

#include "Widget.h"
#include 

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    teacherZhang = new Teacher(this);
    studentWang = new Student(this);
    
    /*可以这么些
     *connect(teacherZhang,SIGNAL(hungry(QString)),studentWang,SLOT(treat(QString)));
     *connect(teacherZhang,SIGNAL(hungry()),studentWang,SLOT(treat()));
    */
    
    //也可以这么写
    //当信号和槽出现函数重载，需要使用函数指针来明确指明函数地址
    //void Teacher::hungry(QString food);带参数函数指针
    void (Teacher::* teacherNoSignal)(void) = &Teacher::hungry;
    //void Student::treat(QString food);带参数函数指针
    void (Student::* studentNoSlot)(void) = &Student::treat;
    connect(teacherZhang,teacherNoSignal,studentWang,studentNoSlot);

    //当信号和槽出现函数重载，需要使用函数指针来明确指明函数地址
    //void Teacher::hungry(QString food);带参数函数指针
    void (Teacher::* teacherSignal)(QString) = &Teacher::hungry;
    //void Student::treat(QString food);带参数函数指针
    void (Student::* studentSlot)(QString) = &Student::treat;
    connect(teacherZhang,teacherSignal,studentWang,studentSlot);

    classOver();

}

Widget::~Widget()
{
}

void Widget::classOver()
{
    emit teacherZhang->hungry();
    emit teacherZhang->hungry("apple");//因为函数指针是带参数的，只有这个被执行
}

main.cpp

#include "Widget.h"

#include 

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
    return a.exec();
}

使用自动连接来试试

    Teacher.h

#ifndef TEACHER_H
#define TEACHER_H

#include 

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

signals:
    void hungry();
    void hungry(QString food);
};

#endif // TEACHER_H

    Teacher.cpp

#include "Teacher.h"

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

}

    Widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include 
#include "Teacher.h"
#include "Student.h"

class Widget : public QWidget
{
    Q_OBJECT

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

private:
    Teacher* teacherZhang;
    Student* studentWang;
public slots:
    void on_teacherZhang_hungry(void);
    void on_teacherZhang_hungry(QString food);
};
#endif // WIDGET_H

Widget.cpp

#include "Widget.h"
#include 
#include 

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    teacherZhang = new Teacher(this);
    teacherZhang->setObjectName(QStringLiteral("teacherZhang"));

    QMetaObject::connectSlotsByName(this);
    
    classOver();
}

void Widget::classOver()
{
    emit teacherZhang->hungry();
    emit teacherZhang->hungry("apple");
}

void Widget::on_teacherZhang_hungry()
{
    qDebug()<<"请老师吃饭"<

#include "Widget.h"
#include 

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
    return a.exec();
}