Change mainwindow ui label text using another class

[mcraellehs]

Hi,

I have a problem, i created a mainwindow UI that has pushbutton and label "text" like in this picture https://prnt.sc/soz9tm
and Rain ui that has pushbutton like in this picture https://prnt.sc/sozbaq

When i compile program, first it opens mainwindow ui and when i clik on pushbutton it opens rain ui.
I want when i click on rain ui's pushbutton to set mainwindow's label text to "It rains",
but i don't know how to access mainwindow's label with Rain's class.

here are my codes and what i tried

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
#include "rain.h"
 
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
 
private slots:
    void on_pushButton_clicked();
 
    public:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include "rain.h"

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private slots:
    void on_pushButton_clicked();

    public:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

To copy to clipboard, switch view to plain text mode 

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
 
void MainWindow::on_pushButton_clicked()
{
    this->hide();
rain *test = new rain();
test->show();
}

#include "mainwindow.h"
#include "ui_mainwindow.h"

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

MainWindow::~MainWindow()
{
    delete ui;
}


void MainWindow::on_pushButton_clicked()
{
    this->hide();
rain *test = new rain();
test->show();
}

To copy to clipboard, switch view to plain text mode 

rain.h

#ifndef RAIN_H
#define RAIN_H
 
#include <QWidget>
#include "mainwindow.h"
 
namespace Ui {
class rain;
}
 
class rain : public QWidget
{
    Q_OBJECT
 
public:
    explicit rain(QWidget *parent = nullptr);
    ~rain();
 
private slots:
    void on_pushButton_clicked();
 
private:
    Ui::rain *ui;
};
 
#endif // RAIN_H

#ifndef RAIN_H
#define RAIN_H

#include <QWidget>
#include "mainwindow.h"

namespace Ui {
class rain;
}

class rain : public QWidget
{
    Q_OBJECT

public:
    explicit rain(QWidget *parent = nullptr);
    ~rain();

private slots:
    void on_pushButton_clicked();

private:
    Ui::rain *ui;
};

#endif // RAIN_H

To copy to clipboard, switch view to plain text mode 

rain.cpp

#include "rain.h"
#include "ui_rain.h"
#include "mainwindow.h"
 
rain::rain(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::rain)
{
    ui->setupUi(this);
 
}
 
rain::~rain()
{
    delete ui;
}
 
void rain::on_pushButton_clicked()
{
    this->hide();
    MainWindow *ma = new MainWindow(this);
 
    ma->show();
}

#include "rain.h"
#include "ui_rain.h"
#include "mainwindow.h"

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

}

rain::~rain()
{
    delete ui;
}

void rain::on_pushButton_clicked()
{
    this->hide();
    MainWindow *ma = new MainWindow(this);

    ma->show();
}

To copy to clipboard, switch view to plain text mode 

[d_stranz]

but i don't know how to access mainwindow's label with Rain's class.

You don't. Implement a signal for your rain class that gets emitted when the user clicks the button. In your MainWindow class, implement a slot to receive this signal. When you create your rain class in MainWindow:: on_pushbutton_clicked(), connect rain's signal to MainWindow's slot.

If you don't understand how to implement custom signals and slots, read the documentation.

Your code as written has a memory leak: Each time your clicked slot is executed, you create a new rain instance. This instance is never destroyed, so it is a memory leak. What you should do instead is make a "rain *" member variable in your MainWindow class, create the rain instance in the MainWindow constructor, and connect the signal and slot. In the clicked slot, simply call show() on this rain instance.

[mcraellehs]

Took some time to learn signal and slot implementation, and i did everything as you said
Thank you, it works perfectly