Qt C++

QT       += core gui
 
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
 
TARGET = untitled
TEMPLATE = app
 
 
SOURCES += main.cpp\
        widget.cpp \
    calc.cpp
 
HEADERS  += widget.h \
    calc.h
 
FORMS    += widget.ui

#ifndef CALC_H
#define CALC_H
 
#include <QObject>
 
class calc : public QObject
{
    Q_OBJECT
public:
    explicit calc(QObject *parent = 0);
 
signals:
 
public slots:
    void func1(int a, int b);
};
 
#endif // CALC_H

#include "calc.h"
#include <QDebug>
 
calc::calc(QObject *parent) : QObject(parent)
{
 
}
 
void calc::func1(int a, int b)
{
    int y = a + b;
    qDebug() << "Result" << y;
}

#ifndef WIDGET_H
#define WIDGET_H
 
#include <QWidget>
#include "calc.h"
 
namespace Ui {
class Widget;
}
 
class Widget : public QWidget
{
    Q_OBJECT
 
public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();
 
    calc *do_calc;
 
public slots:
    void prepare_data();
 
signals:
    void send_data_for_calc(int a, int b);
 
private:
    Ui::Widget *ui;
};
 
#endif // WIDGET_H

#include "widget.h"
#include "ui_widget.h"
 
Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
    do_calc = new calc;
    connect(ui->pushButton, SIGNAL(clicked(bool)), this, SLOT(prepare_data()));
    connect(this, SIGNAL(send_data_for_calc(int,int)), do_calc, SLOT(func1(int,int)));
}
 
Widget::~Widget()
{
    delete do_calc;
    delete ui;
}
 
void Widget::prepare_data()
{
    int a = 0;
    int b = 5;
    emit send_data_for_calc(a, b);
}

#include "widget.h"
#include <QApplication>
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
 
    return a.exec();
}