QT signal and slot

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Preface

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One 、 Signals and slots

Signals and slots are used for communication between objects , It is similar to the interface address between the back end and the front end .
The signal is sent by the sender , The slot can be regarded as the receiver
The signal and slot are QT Unique signal transmission mechanism , He can make contact with objects that do not interfere with each other
utilize connect Function creation
The essence of a slot is a member function of a class , Its parameters can be of any type and C++ Member functions make no difference . It can be a virtual function , Can also be overloaded ,
The only difference is that the slot can be connected with the signal ,, Whenever the signal connected to the slot is sent, it will call the slot
You can also send signals , Then do the corresponding operation before sending to the slot

Characteristics of signal :

Ordinary function , There is no need to achieve , Use signal Keyword declaration , You can customize the signal , no return value , With parameters , Can be suitable for use emit Keywords send signals

Characteristics of grooves

Customizable slot function
Slot function has no return value
With parameters

Two 、 Connect

1、QT4

Through macro
SIGNAL SLOT
SLGNAL()/SLOT Two Hongjiang functions rotate -> character string
connect(sender,SLGNAL(sig1(int,double,QString)),receiver,SLOT(sil1(int,doublemQString)))
shortcoming Error checking will not be done during compilation

2、QT5

The function address used by the signal slot
connect(sender,&Sender::sig1,receiver,&Receiver::slot1)
advantage During compilation, the function type , Check the number

The code is as follows （ Example ）：

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
import warnings
warnings.filterwarnings('ignore')
import  ssl
ssl._create_default_https_context = ssl._create_unverified_context

Four 、 matters needing attention

The signal / The number of slot function parameters can be different
The number of slot function parameters can be less than the number of signal parameters
Irreversible

5、 ... and 、 Expand

Signals can be connected to signals
One signal can connect multiple slot functions
A slot function can be connected by multiple signals at the same time
Slot functions can be used lambda expression
After the signal slot is connected , Can be disconnected disconnect

The following is written in the main function , Other creation items are automatically added , Just copy the following code to the main cpp Just fine
The sample code be based on QT4

#include "widget.h"
#include <QPushButton>
Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    
    QPushButton *btn = new QPushButton("adsdadww ",this);
    btn->show();
    btn->resize(50,50);
    btn->move(60,60);
    resize(600,400);

    QPushButton *btn2 = new QPushButton("slfeofs",this);
    btn2->show();
    btn2->resize(80,30);
    btn2->move(100,100);
    this->zt = new Teacher(this);
    this->st = new Student(this);



   connect(btn2,SIGNAL(clicked()),zt,SIGNAL(hungry()));
   connect(zt,SIGNAL(hungry()),st,SLOT(treat()));
   connect(btn2,SIGNAL(clicked()),this,SLOT(close()));
   st->treat();

    setWindowTitle("sdawadwd");
    setFixedSize(600,400);



    //connect(st,SLOT(treat()));



}
void Widget::classIsOver(){
    

}
Widget::~Widget()
{
    

}

 be based on QT5 Code for 

#include "mainwindow.h"
#include <QPushButton>
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    
    QPushButton *btn = new QPushButton("adsdadww ",this);
    btn->show();
    btn->resize(50,50);
    btn->move(60,60);
    resize(600,400);

    QPushButton *btn2 = new QPushButton("slfeofs",this);
    btn2->show();
    btn2->resize(30,30);
    btn2->move(100,100);




 connect(btn2,&QPushButton::clicked,this,&MainWindow::close);

    setWindowTitle("sdawadwd");
    setFixedSize(600,400);

}

MainWindow::~MainWindow()
{
    

}