General: Structure of a Qt mainwindow program

[victor.fernandez]

There are two ways. You may subclass the Ui::MainWindow class or have it as a class member. I personally prefer the first way but it's mostly a matter of taste.

The first one (the multiple inheritance approach):

mainwindow.h

#include "ui_mainwindow.h"
 
class MainWindow : public QMainWindow, private Ui::MainWindow
{
    Q_OBJECT
 
public:
    MainWindow(QWidget *parent = 0);
 
protected slots:
    void sayHello();
};

#include "ui_mainwindow.h"

class MainWindow : public QMainWindow, private Ui::MainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);

protected slots:
    void sayHello();
};

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mainwindow.cpp

#include "mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent)
 : QMainWindow(parent)
{
    setupUi(this);
 
    connect(m_myButton, SIGNAL(clicked()),
            this, SLOT(sayHello()));
}
 
void MainWindow::sayHello()
{
    m_myLineEdit->setText(tr("Hello world"));
}

#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
 : QMainWindow(parent)
{
    setupUi(this);

    connect(m_myButton, SIGNAL(clicked()),
            this, SLOT(sayHello()));
}

void MainWindow::sayHello()
{
    m_myLineEdit->setText(tr("Hello world"));
}

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For the second way (the single inheritance approach):

mainwindow.h

#include "ui_mainwindow.h"
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    MainWindow(QWidget *parent = 0);
 
protected slots:
    void sayHello();
 
private:
    Ui::MainWindow ui;
};

#include "ui_mainwindow.h"

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);

protected slots:
    void sayHello();

private:
    Ui::MainWindow ui;
};

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mainwindow.cpp

#include "mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent)
 : QMainWindow(parent)
{
    ui.setupUi(this);
 
    connect(ui.m_myButton, SIGNAL(clicked()),
            this, SLOT(sayHello()));
}
 
void MainWindow::sayHello()
{
    ui.myLineEdit->setText(tr("Hello world"));
}

#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
 : QMainWindow(parent)
{
    ui.setupUi(this);

    connect(ui.m_myButton, SIGNAL(clicked()),
            this, SLOT(sayHello()));
}

void MainWindow::sayHello()
{
    ui.myLineEdit->setText(tr("Hello world"));
}

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More details.