Access to the form through the slot, how?

Question

Qt

When you try to access widgets on the form through the slot, nothing happens. Perhaps this is how it should be?

form.cpp

#include "form.h"
        #include "ui_form.h"
        #include<mainwindow.h>
        Form::Form(QWidget *parent) :
            QWidget(parent),
            ui(new Ui::Form)
        {
            ui->setupUi(this);
            MainWindow* m = new MainWindow;
            connect(ui->pushButton, SIGNAL(clicked(bool)), this, SLOT(send()));
            connect(this, SIGNAL(sendData(QString)) ,m, SLOT(textchanged(QString)) );
        }

        Form::~Form()
        {
            delete ui;
        }
        void Form::send(){
            emit sendData(ui->lineEdit->text());
        }

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include<form.h>
#include<ui_form.h>.
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
   // Form* form = new Form;
    connect(ui->pushButton , SIGNAL(clicked()) , this, SLOT(showadd()));
}

MainWindow::~MainWindow()
{
    delete ui;
}
void MainWindow::textchanged(QString data){
    ui->lineEdit->setText(data);
}
void MainWindow::showadd(){
     Form* form = new Form;
     form->show();
}

form.h

#ifndef FORM_H
#define FORM_H

#include <QWidget>

namespace Ui {
class Form;
}

class Form : public QWidget
{
    Q_OBJECT

public:
    explicit Form(QWidget *parent = nullptr);
    ~Form();
public slots:
    void send();
signals:
    void sendData(QString data);
private:
    Ui::Form *ui;
};

#endif // FORM_H

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
public slots:
    void textchanged(QString data);
    void showadd();
private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

main.cpp

#include "mainwindow.h"

#include <QApplication>

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

Answer 1

At least what I see
1. The MainWindow form is created and deleted immediately in the constructor It is
necessary to declare the class in form.h
...
private:
Ui::Form *ui;
MainWindow *m;
};
initialize before connect in form.cpp
...
{
ui->setupUi(this);
m = new MainWindow;
connect(ui->pushButton, SIGNAL(clicked(bool)), this, SLOT(send()));
connect(this, SIGNAL(sendData(QString)) ,m, SLOT(textchanged(QString)) );
...
2. After the first paragraph, you can remove the extra connection and directly call the method
in form.h
...
{
ui->setupUi(this);
m = new MainWindow;
connect(ui->pushButton, SIGNAL(clicked(bool)), this, SLOT(send()));
connect(this, SIGNAL(sendData(QString)) ,m, SLOT(textchanged(QString)) );
...
void Form::send(){
emit sendData(ui->lineEdit->text());
m->textchanged(ui->lineEdit->text());
}
...