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connect(信号发送者，发送的信号，信号接收者，信号的处理);

信号函数和槽函数的参数必须是一样的，但信号的参数可以多余槽函数的参数（前面的参数类型必须一致）

是控件和控件间的信号传递，这两个之间没有关联，松散耦合

两个连接意义相同，用父类的（发送的信号，或信号的处理（要地址））或自己类名都可以

//自定义类MyButton 继承QPushButton
MyButton *but=new MyButton;
but->setText("hhh");
but->setParent(this);
connect(but,&MyButton::clicked,this,&MainWindow::close);
connect(but,&QPushButton::clicked,this,&QMainWindow::close);

自定义信号和槽

自定义信号：//不用在.cpp里实现faSingnals();

.h
class fasong : public QObject
{Q_OBJECT
public:explicit fasong(QObject *parent = nullptr);signals:
//自定义信号//没有返回值的只需要声明不需要实现，可以有参数可以重载//信号函数void faSingnals();void faSingnals(QString string);
};

自定义槽：

.h
class jieshou : public QObject
{Q_OBJECT
public:explicit jieshou(QObject *parent = nullptr);signals:public slots://槽函数//返回void 需要声明和实现，可以有参数可以重载//槽函数void shouSlots();void shouSlots(QString string);
};

//需要在.cpp里实现shouSlots()函数；

#include "jieshou.h"
#include <QtDebug>
jieshou::jieshou(QObject *parent) : QObject(parent)
{}
void jieshou::shouSlots()
{qDebug()<<"你好";
}
void jieshou::shouSlots(QString string)
{//先toUtf8()转成ByteArray在.data()转成char*()//输出的字符串不带引号qDebug()<<string.toUtf8().data();
}

可以理解为这里的主函数：调用信号和槽

.h
#include"fasong.h"
#include"jieshou.h"
#include <QMainWindow>QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACEclass MainWindow : public QMainWindow
{Q_OBJECTpublic:MainWindow(QWidget *parent = nullptr);~MainWindow();private:Ui::MainWindow *ui;///触发信号void chuFa();///信号对象fasong *fa;///槽对象jieshou *shou;
};

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QPushButton>
#include "MyButton.h"
MainWindow::MainWindow(QWidget *parent): QMainWindow(parent), ui(new Ui::MainWindow)
{ui->setupUi(this);//发送者对象this->fa=new fasong(this);//接收者对象this->shou=new jieshou(this);//连接信号与槽//connect(fa,&fasong::faSingnals,shou,&jieshou::shouSlots);//信号与槽有重载时的连接方法//函数指针指向函数地址void(fasong:: *faSongDiZhi)(QString)=&fasong::faSingnals;void(jieshou:: *jieshouDiZhi)(QString)=&jieshou::shouSlots;//连接信号与槽（有参）connect(fa,faSongDiZhi,shou,jieshouDiZhi);//实现点击按钮触发 触发信号QPushButton *button=new QPushButton;button->setParent(this);button->setText("Button1");//绑定按钮点击触发触发信号connect(button,&QPushButton::clicked,this,&MainWindow::chuFa);void(fasong:: *faSongDiZhi1)(void)=&fasong::faSingnals;void(jieshou:: *jieshouDiZhi1)(void)=&jieshou::shouSlots;//信号连接信号connect(button,&QPushButton::clicked,fa,faSongDiZhi1);//发送和接收连接（无参）信号和槽连接connect(fa,faSongDiZhi1,shou,jieshouDiZhi1);//断开信号,怎么连接就怎么断开disconnect(button,&QPushButton::clicked,fa,faSongDiZhi1);chuFa();}///触发信号
void MainWindow::chuFa()
{//emit触发关键字,faSingnals为信号函数//emit fa->faSingnals();emit fa->faSingnals("哈哈哈");
}MainWindow::~MainWindow()
{delete ui;
}

输出：

//有参
connect(fa,SIGNAL(faSingnals(QString)),shou,SLOT(shouSlots(QString)));

//无参
connect(fa,SIGNAL(faSingnals()),shou,SLOT(shouSlots()));

不建议使用