cannot call member function 'void window::updateStatus(QString)' without object

[Astrognome]

I've been googling for a while, and I can find no solution to my problem. I want to access items in the ui from different files, but haven't had any luck. But anyway here's the code:

main.cpp

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

#include <QtGui/QApplication>
#include "window.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    window w;
    w.show();
    
    return a.exec();
}

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window.cpp

#include "window.h"
#include "ui_window.h"
#include "worldBackup.h"
 
#include <QString>
 
window::window(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::window)
{
    ui->setupUi(this);
}
 
window::~window()
{
    delete ui;
}
 
void window::updateStatus(QString text)
{
    ui->statusBar->setText(text);
}
 
void window::on_quitButton_clicked()
{
    listWorlds();
}

#include "window.h"
#include "ui_window.h"
#include "worldBackup.h"

#include <QString>

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

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

void window::updateStatus(QString text)
{
    ui->statusBar->setText(text);
}

void window::on_quitButton_clicked()
{
    listWorlds();
}

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worldBackup.cpp

#include "window.h"
//#include "ui_window.h"
 
bool listWorlds(){
    window::updateStatus("Status: Quitting...");
    return true;
}

#include "window.h"
//#include "ui_window.h"

bool listWorlds(){
    window::updateStatus("Status: Quitting...");
    return true;
}

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window.h

#ifndef WINDOW_H
#define WINDOW_H
 
#include <QWidget>
 
namespace Ui {
class window;
}
 
class window : public QWidget
{
    Q_OBJECT
 
public:
    explicit window(QWidget *parent = 0);
    ~window();
 
    void updateStatus(QString text);
 
private slots:
    void on_quitButton_clicked();
 
private:
    Ui::window *ui;
};
 
#endif // WINDOW_H

#ifndef WINDOW_H
#define WINDOW_H

#include <QWidget>

namespace Ui {
class window;
}

class window : public QWidget
{
    Q_OBJECT
    
public:
    explicit window(QWidget *parent = 0);
    ~window();

    void updateStatus(QString text);

private slots:
    void on_quitButton_clicked();

private:
    Ui::window *ui;
};

#endif // WINDOW_H

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worldBackup.h

#ifndef WORLDBACKUP_H
#define WORLDBACKUP_H
 
bool listWorlds();
 
#endif // WORLDBACKUP_H

#ifndef WORLDBACKUP_H
#define WORLDBACKUP_H

bool listWorlds();

#endif // WORLDBACKUP_H

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The error is thrown by line 5 of backupWorld.cpp