pointer at QMainWindow

[mattia]

Hello, if i have created with QT Designer a class called ui_class.h with the main window layout and at the and i have declared this namespace:

namespace Ui {
    class MainWindowClass: public Ui_MainWindowClass {};
}

namespace Ui {
    class MainWindowClass: public Ui_MainWindowClass {};
}

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then i've made class.h in this way

#include <QtGui/QWidget>
#include "modify.h"
class class : public QMainWindow
{
    Q_OBJECT
 
public:
    class();
    ~class();
private:
    Ui::MainWindowClass ui;
    Modify *modify;
};

#include <QtGui/QWidget>
#include "modify.h"
class class : public QMainWindow
{
    Q_OBJECT

public:
    class();
    ~class();
private:
    Ui::MainWindowClass ui;
    Modify *modify;
};

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and the class.cpp

#include <QtGui>
#include "class.h"
 
 
class::class()
{
	ui.setupUi(this);
	modify = new Modify(this);
 
}
 
server::~server(){}

#include <QtGui>
#include "class.h"


class::class()
{
	ui.setupUi(this);
	modify = new Modify(this);
	
}

server::~server(){}

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how is the constructor in modify.h? cos i want to pass at the modify.h a pointer at the "MainWindowClass ui" to have access at all the widget that i have in ui_class.h.
Is it possibile?

[wysota]

What is Modify? If it is your class, you can implement a constructor that fits your needs and pass it the pointer you need.

[mattia]

What is Modify? If it is your class, you can implement a constructor that fits your needs and pass it the pointer you need.

Yes, it is my class. How would the constructor be?

Modify::Modify(...){} //<-- ??

Modify::Modify(...){} //<-- ??

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Then i'd like to have access at all the Widget elements into the ui_class.h.
Thanks

[jpn]

class class : public QMainWindow

class class : public QMainWindow

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Is this legal C++?

[mattia]

No, it isn't legal in C++ but i was making just an example and i didn't pay attention at the class name, next time i'll take care about it cos i know i can generate misconception

[wysota]

Make the constructor accept a pointer to QMainWindow (just like QWidgets accept a pointer to QWidgets) and store the pointer somewhere in Modify.

[mattia]

I'made a little example to explain me in the best way, I created a simple GUI with a menu and a label, when i click on the menu voice i'd like to change the text label. To do this i created a class doSmt.h that perform this work.
I want to pass a QMainWindow pointer to the class doSmt to have the access at all the attributes defined in ui_guiwid.h.
In the class guiwid i cant acces to them simply with ui.nomeAttribute, i'd like to do the same thing into doSmt class. Thx

ui_guiwid.h

#ifndef UI_GUIWID_H
#define UI_GUIWID_H
 
#include <QtCore/QVariant>
#include <QtGui/QAction>
#include <QtGui/QApplication>
#include <QtGui/QButtonGroup>
#include <QtGui/QLabel>
#include <QtGui/QMainWindow>
#include <QtGui/QMenu>
#include <QtGui/QMenuBar>
#include <QtGui/QStatusBar>
#include <QtGui/QWidget>
 
class Ui_MainWindow
{
public:
    QAction *actionChangeLabel;
    QWidget *centralwidget;
    QLabel *label;
    QMenuBar *menubar;
    QMenu *menuFIle;
    QStatusBar *statusbar;
 
    void setupUi(QMainWindow *MainWindow)
    {
    if (MainWindow->objectName().isEmpty())
        MainWindow->setObjectName(QString::fromUtf8("MainWindow"));
    MainWindow->resize(420, 510);
    actionChangeLabel = new QAction(MainWindow);
    actionChangeLabel->setObjectName(QString::fromUtf8("actionChangeLabel"));
    centralwidget = new QWidget(MainWindow);
    centralwidget->setObjectName(QString::fromUtf8("centralwidget"));
    label = new QLabel(centralwidget);
    label->setObjectName(QString::fromUtf8("label"));
    label->setGeometry(QRect(20, 10, 321, 21));
    MainWindow->setCentralWidget(centralwidget);
    menubar = new QMenuBar(MainWindow);
    menubar->setObjectName(QString::fromUtf8("menubar"));
    menubar->setGeometry(QRect(0, 0, 420, 28));
    menuFIle = new QMenu(menubar);
    menuFIle->setObjectName(QString::fromUtf8("menuFIle"));
    MainWindow->setMenuBar(menubar);
    statusbar = new QStatusBar(MainWindow);
    statusbar->setObjectName(QString::fromUtf8("statusbar"));
    MainWindow->setStatusBar(statusbar);
 
    menubar->addAction(menuFIle->menuAction());
    menuFIle->addAction(actionChangeLabel);
 
    retranslateUi(MainWindow);
 
    QMetaObject::connectSlotsByName(MainWindow);
    } // setupUi
 
    void retranslateUi(QMainWindow *MainWindow)
    {
    MainWindow->setWindowTitle(QApplication::translate("MainWindow", "MainWindow", 0, QApplication::UnicodeUTF8));
    actionChangeLabel->setText(QApplication::translate("MainWindow", "Change Label", 0, QApplication::UnicodeUTF8));
    label->setText(QApplication::translate("MainWindow", "TextLabel", 0, QApplication::UnicodeUTF8));
    menuFIle->setTitle(QApplication::translate("MainWindow", "File", 0, QApplication::UnicodeUTF8));
    } // retranslateUi
 
};
 
namespace Ui {
    class MainWindow: public Ui_MainWindow {};
} // namespace Ui
 
#endif // UI_GUIWID_H

#ifndef UI_GUIWID_H
#define UI_GUIWID_H

#include <QtCore/QVariant>
#include <QtGui/QAction>
#include <QtGui/QApplication>
#include <QtGui/QButtonGroup>
#include <QtGui/QLabel>
#include <QtGui/QMainWindow>
#include <QtGui/QMenu>
#include <QtGui/QMenuBar>
#include <QtGui/QStatusBar>
#include <QtGui/QWidget>

class Ui_MainWindow
{
public:
    QAction *actionChangeLabel;
    QWidget *centralwidget;
    QLabel *label;
    QMenuBar *menubar;
    QMenu *menuFIle;
    QStatusBar *statusbar;

    void setupUi(QMainWindow *MainWindow)
    {
    if (MainWindow->objectName().isEmpty())
        MainWindow->setObjectName(QString::fromUtf8("MainWindow"));
    MainWindow->resize(420, 510);
    actionChangeLabel = new QAction(MainWindow);
    actionChangeLabel->setObjectName(QString::fromUtf8("actionChangeLabel"));
    centralwidget = new QWidget(MainWindow);
    centralwidget->setObjectName(QString::fromUtf8("centralwidget"));
    label = new QLabel(centralwidget);
    label->setObjectName(QString::fromUtf8("label"));
    label->setGeometry(QRect(20, 10, 321, 21));
    MainWindow->setCentralWidget(centralwidget);
    menubar = new QMenuBar(MainWindow);
    menubar->setObjectName(QString::fromUtf8("menubar"));
    menubar->setGeometry(QRect(0, 0, 420, 28));
    menuFIle = new QMenu(menubar);
    menuFIle->setObjectName(QString::fromUtf8("menuFIle"));
    MainWindow->setMenuBar(menubar);
    statusbar = new QStatusBar(MainWindow);
    statusbar->setObjectName(QString::fromUtf8("statusbar"));
    MainWindow->setStatusBar(statusbar);

    menubar->addAction(menuFIle->menuAction());
    menuFIle->addAction(actionChangeLabel);

    retranslateUi(MainWindow);

    QMetaObject::connectSlotsByName(MainWindow);
    } // setupUi

    void retranslateUi(QMainWindow *MainWindow)
    {
    MainWindow->setWindowTitle(QApplication::translate("MainWindow", "MainWindow", 0, QApplication::UnicodeUTF8));
    actionChangeLabel->setText(QApplication::translate("MainWindow", "Change Label", 0, QApplication::UnicodeUTF8));
    label->setText(QApplication::translate("MainWindow", "TextLabel", 0, QApplication::UnicodeUTF8));
    menuFIle->setTitle(QApplication::translate("MainWindow", "File", 0, QApplication::UnicodeUTF8));
    } // retranslateUi

};

namespace Ui {
    class MainWindow: public Ui_MainWindow {};
} // namespace Ui

#endif // UI_GUIWID_H

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guiwid.h

#include <QtGui/QWidget>
#include "ui_guiwid.h"
 
class guiwid : public QMainWindow
{
    Q_OBJECT
 
public:
    guiwid();
    ~guiwid();
private slots:
	void callDoStm();
private:
    Ui::MainWindow ui;
};

#include <QtGui/QWidget>
#include "ui_guiwid.h"

class guiwid : public QMainWindow
{
    Q_OBJECT

public:
    guiwid();
    ~guiwid();
private slots:
	void callDoStm();
private:
    Ui::MainWindow ui;
};

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guiwid.cpp

#include "guiwid.h"
#include "doSmt.h"
#include <QtGui/QWidget>
 
guiwid::guiwid()
{
	ui.setupUi(this);
	connect(ui.actionChangeLabel, SIGNAL(triggered()), this, SLOT(callDoStm()));
}
 
guiwid::~guiwid()
{
 
}
 
void guiwid::callDoStm(){
	doSmt *ds = new doSmt(this);
	ds->changeLabel();
}

#include "guiwid.h"
#include "doSmt.h"
#include <QtGui/QWidget>

guiwid::guiwid()
{
	ui.setupUi(this);
	connect(ui.actionChangeLabel, SIGNAL(triggered()), this, SLOT(callDoStm()));
}

guiwid::~guiwid()
{

}

void guiwid::callDoStm(){
	doSmt *ds = new doSmt(this);
	ds->changeLabel();
}

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doSmt.h

#include <QtGui/QWidget>
#include <QMainWindow>
 
class doSmt 
{
public:
    doSmt(QMainWindow *ui);
    ~doSmt(); 	
public:
	void changeLabel();
	QMainWindow *mainWindow;
};

#include <QtGui/QWidget>
#include <QMainWindow>

class doSmt 
{
public:
    doSmt(QMainWindow *ui);
    ~doSmt(); 	
public:
	void changeLabel();
	QMainWindow *mainWindow;
};

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doSmt.cpp

#include "doSmt.h"
#include <QtGui/QWidget>
 
doSmt::doSmt(QMainWindow *ui)
{
	this->mainWindow = ui;
}
 
doSmt::~doSmt()
{
 
}
 
void doSmt::changeLabel()
{
	// i can't access to the MainWindow attributes with mainWindow-> 
}

#include "doSmt.h"
#include <QtGui/QWidget>

doSmt::doSmt(QMainWindow *ui)
{
	this->mainWindow = ui;
}

doSmt::~doSmt()
{

}

void doSmt::changeLabel()
{
	// i can't access to the MainWindow attributes with mainWindow-> 
}

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[wysota]

1. Do you need doSmt::changeLabel() to be a separate class? You can have the same functionality in guiwnd.

2. Your problem is strictly C++ related. The ui component is private, thus other objects don't have access to it. You can either declare the doSmt class friend to the guiwnd class (not recommended), move the ui component to public section or use multiple inheritance approach (not recommended) or provide public methods (they are called getters and setters) in guiwnd to access components of the ui (that's what Qt does and preferrs). Of course you'll also need to cast that QMainWindow pointer to guiwnd pointer to be able to access its fields and methods (or better yet make your constructor accept a pointer to guiwnd instead of QMainWindow).

[mattia]

Thanks for the explanation, no i don't need a separate class to change a label, i thought that when i'll work with more complex application maybe i'll need to get access at some elements defined into ui_guiwid.h and rather than pass all the elements at the classes that will modify them it would be better get the direct access through a pointer to main window.
I've solved it passed Ui::MainWindow ui; as pointer to doStm and i'm storing it into the class as private member. Do you think it is a smart way?
Thx

[wysota]

No, it's not a smart way - it breaks the Object Oriented Programming paradigm. First you make the ui private so that noone can access it and then you allow some other object to modify it behind your back. With Qt you should just use signals and slots, like so:

class Parent : public QWidget{
public:
  Parent(QWidget *parent=0) : QWidget(parent){
    ui.setupUi(this);
    obj = new childClass;
    connect(obj, SIGNAL(changeLabelText(const QString &)), ui.someLabel, SLOT(setText(const QString &)));
  }
  ~Parent(){}
private:
  Ui::someUi ui;
  childClass *obj;
};

class Parent : public QWidget{
public:
  Parent(QWidget *parent=0) : QWidget(parent){
    ui.setupUi(this);
    obj = new childClass;
    connect(obj, SIGNAL(changeLabelText(const QString &)), ui.someLabel, SLOT(setText(const QString &)));
  }
  ~Parent(){}
private:
  Ui::someUi ui;
  childClass *obj;
};

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[mattia]

I followed your useful suggestions Thanks so much!