Communicate with non-member function

[R_Irudezu]

It might not be that difficult.. Just sending data from global function to UI Window.

void generateData(params)
{
    // the data generated here needs to be passed to UI window
}

UI section:

Use these data as QPainter function parameters. That's all but how to do..

[dheerendra]

Assuming that generateData(..) function is written by you. Add new class in Called DataGenerator inherit from QObject. Create the DataGenerator object as global object. This object should be accessible from both your callback() and MainWIndow class.

Define the method acceptData(x,y), in DataGenerator which is called whenever callback is called.
Define the signal in DataGenerator. Send this signal from acceptData(..) method.
Catch this signal in in your mainWindow.

In summary you have QObject class which acts as intermediately between your call back and MainWindow.

[R_Irudezu]

So i did like:
(mainwindow.h)

#include <QMainWindow>
#include <QObject>

namespace Ui {
class MainWindow;
class dataSender; // which you mean DataGenerator Class
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private:
    Ui::MainWindow *ui;

};

class dataSender: public QObject
{
    Q_OBJECT

public:

    int acceptData(int *getx, int *gety)
    {
        int acceptedData = *get;
        return acceptedData;
    }

    dataSender(QObject * parent) : QObject(parent)
    {
        dataSender* parent= qobject_cast<dataSender*>(parent);

        // i don't know how to use here @dheerendra 
        if (parent)
            QObject::connect(parent, SIGNAL(acceptDataSignal()), this, SIGNAL(acceptDataSignal()));
       
    }

signals:
    
    void acceptDataSignal();

};

#endif // MAINWINDOW_H

(mainwindow.cpp)

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

// here my global callback function
// i mean yes your assume is right, i am gonna write this function and it will generate data
void callBack(int *x, int *y)
{
    /* this values will be change every second, i just want to see them change in 
       UI QLabel or TextEdit widget 
    */

    x += 5;
    y += 10;
}

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

    // here data must be shown in label and i want to see them change every second
    ui->testLabel->text = "x is" + x + "and y is " + y;
}

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

so what now, i really do not know how to use signal and slot in this case.

[dheerendra]

See the following program and use it.

class GenerateData : public QObject
{
Q_OBJECT
public:
explicit GenerateData(QObject *parent = nullptr);
void display();
signals:
void sendData(int x, int y);
public slots:
};

#include "GenerateData.h"

GenerateData::GenerateData(QObject *parent) : QObject(parent)
{

}

void GenerateData::display()
{
qDebug() << Q_FUNC_INFO << endl;
emit sendData(10,20);
}
class MyWidget : public QWidget
{
Q_OBJECT

public:
explicit MyWidget(QWidget *parent = 0);
~MyWidget();
void display();
void setGenerator(GenerateData *d1);

public slots :
void plotData(int x, int y);

private:
Ui::MyWidget *ui;
GenerateData *dg;
};

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

MyWidget::~MyWidget()
{
delete ui;
}
void MyWidget::setGenerator(GenerateData *d1)
{
this->dg = d1;
connect(this->dg,SIGNAL(sendData(int,int)),this,SLOT(plotData(int,int)));
}

void MyWidget::plotData(int x, int y)
{
qDebug() << " X=" << y << " Y =" << y <<endl;
}

========main.cpp============
#include "MyWidget.h"
#include "GenerateData.h"
#include <QApplication>

GenerateData d;

void callme(MyWidget *w) {
std::cout << " Welcome to all" << endl;
d.display();
}

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MyWidget w;
w.show();
w.setGenerator(&d);
callme(&w);

return a.exec();

}

[R_Irudezu]

@dheerendra this code works thanks but when i use in the MainWindow's constructor or in a button slot such as:

void MainWindow::on_pushButton_clicked()
{
    MainWindow w;
    w.setGenerator(&d);
    callme(&w);
}

when i run it, it gives SIGSEGV error. How can i use this object in MainWindow.cpp not in main.cpp

[dheerendra]

You are creating the stack object and hence crashes. Create the dynamic object like the following.

MainWindow *w = new MainWindow;
w->setGenerator(&d);
callme(w);

[R_Irudezu]

@dheerendra Thank you for all your help sir!

[dheerendra]

Move this issue to solved state, if it already solved the problem.

[R_Irudezu]

@dheerendra I already did.

[dheerendra]

MainWindow *w = new MainWindow;

Make the variable w as member variable. Then delete it when you don't require the object any more.