QT - Swapping Icons

Question

I made a simple program to demonstrate my issues with attempting to use the QIcon swap() function. I am trying to swap the icons on two QPushButtons using this function, but it doesnt seem to be working.

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QPushButton>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

public slots:
    void swap_icons();

private:
    Ui::MainWindow *ui;

    QPushButton *buttons[2];
};

#endif // MAINWINDOW_H

mainwindow.cpp

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

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    buttons[0] = new QPushButton(QString::number(0), this);
    buttons[1] = new QPushButton(QString::number(1), this);

    QPixmap pix(":/BP.PNG");
    QIcon icon(pix);

    buttons[0]->move(100,100);
    buttons[0]->setIcon(icon);
    buttons[0]->setIconSize(pix.size());

    connect(buttons[0], SIGNAL(clicked()), this, SLOT(swap_icons()));

    QPixmap pix2(":/BR.PNG");
    QIcon icon2(pix2);
    buttons[1]->setIcon(icon2);
    buttons[1]->setIconSize(pix.size());


}

void MainWindow::swap_icons() {
    buttons[0]->icon().swap(buttons[1]->icon());
}

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

When I push buttons[0], the icons do not swap. They remain the same.

Answer 1

You do not set the new icon. I think it should be like:

buttons[0]->setIcon(buttons[0]->icon().swap(buttons[1]->icon()));

However this will change only the first button's icon.

I would write it in more simple way, which is easier to read and understand:

QIcon tmp = buttons[0]->icon();
buttons[0]->setIcon(buttons[1]->icon());
buttons[1]->setIcon(tmp);