Forward Declaration error

stima_ua

Its example.

//mainwindow.h
@
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

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

private:
Ui::MainWindow *ui;
};

#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);

//use ui: ui->button->setText("Text");

}

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

@

--------or-------------
//mainwindow.h
@
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include "ui_mainwindow.h"

class MainWindow : public QMainWindow, public Ui_MainWindow
{
Q_OBJECT

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

private:

};

#endif // MAINWINDOW_H
@

//mainwindow.cpp
@
#include "mainwindow.h"

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

//use ui: button->setText("Text");

}

MainWindow::~MainWindow()
{
}
@

r3willia

[quote author="pragati" date="1337334158"] Using now namespace Ui, still getting error:

/home/pragati/MultiFuncTester/Components/DMM/Build/../Source/DMM.cpp:14: error: 'class DMM::Ui::DMMMenu' has no member named 'setupUi'[/quote]

In the example posted by stima_ua, the Ui namespace is being used by the resources framework to generate a Ui::MainWindow class definition. This is the same as in your case - the DMM_ui.h generates a class definition called Ui::DMMMenu - there is nothing called DMM::Ui::DMMMenu defined. However, in your header DMM.h, you have told the compiler that there's a forward declaration for a type DMM::Ui::DMMMenu - you then use this as the type of your pointer with the lines:
@private:

Ui::DMMMenu *ui;@

Bear in mind - this is telling the compiler: "I want a pointer of type DMM::Ui::DMMMenu" because you're making this declaration from within the DMM namespace.

If you want to do your implementation using the UI resources from Qt, you'll need to do your declaration like this:
@
namespace Ui {

class DMMMenu;

}

namespace DMM {

class DMMMenu: public QWidget
{
Q_OBJECT

public:

explicit DMMMenu(QWidget *parent = 0);
~DMMMenu();

private:

::Ui::DMMMenu *ui;

};

}@

This tells the compiler that it will receive a full declaration of Ui::DMMMenu later on, and that you want to use Ui::DMMMenu as the type for your ui member pointer in your DMM::DMMMenu class declaration.

pragati

I did as you guys told

@
namespace Ui {

class DMMMenu;

}

namespace DMM {

class DMMMenu: public QWidget
{
Q_OBJECT

public:

explicit DMMMenu(QWidget *parent = 0);
~DMMMenu();

private:

::Ui::DMMMenu *ui;

};

}@

But now the compiler is telling the prototype in dmm.cpp and dmm_ui.h doesnot match

r3willia

I think that's progress. What's the exact message you're seeing?

pragati

:).....

1 /home/pragati/MultiFuncTester/Components/DMM/Build/../Source/DMM.cpp:8: error: prototype for 'Ui::DMMMenu::DMMMenu(QWidget*)' does not match any in class 'Ui::DMMMenu'

/home/pragati/MultiFuncTester/Components/DMM/Build/ui_DMM.h:61: error: candidates are: Ui::DMMMenu::DMMMenu(const Ui::DMMMenu&)

error: Ui::DMMMenu::DMMMenu()

r3willia

From the code you've posted of DMM_ui.h, Ui::DMMMenu has no explicit constructor - this means the compiler will have given it an implicit copy constructor of signature Ui::DMMMenu::DMMMenu(const Ui::DMMMenu&) This is the candidate you're seeing.

Do you still use the Ui namespace in your DMM.cpp file? It looks like the compiler's trying to link DMM::DMMMenu against Ui::DMMMenu!

Make sure if there's any ambiguity that you remove it by explicitly specifying the name of the type you're using. Is your code in DMM.cpp now looking something like this?
@
# include <../Include/DMM.h>
# include <ui_DMM.h>

namespace DMM {
 
DMMMenu::DMMMenu(QWidget *parent) :
    QWidget(parent),
    ui(new ::Ui::DMMMenu)
{
    ui->setupUi(this);
}
 
}@

pragati

I did changed to Namespace DMM...but prob is I have to create an instance of this DMM in other directory class like this:
Start.h
@
#ifndef START_H
#define START_H

#include "../../DMM/Include/DMM.h"

/****************************************************************************/
/**

\brief This class handles the initialization of the user interface.
/
/***************************************************************************/
namespace Start {

class Startup : public QObject
{
Q_OBJECT

public:
Startup();
virtual ~Startup();
void GuiInit();

private:

Ui::DMMMenu *MainWindow;

};

}

#endif // START_H
@

Start.cpp:

@

#include "../../Start/Include/Start.h"

namespace Start {

Startup::Startup() : QObject()
{

// GUI components

MainWindow = new DMM::DMMMenu();

}

Startup::~Startup()
{
try {
// GUI Components

    delete MainWindow;
}
catch (...) {}

}

/***************************************************************************/
/!

\brief Initializes the user interface
/
/***************************************************************************/
void Startup::GuiInit()
{
MainWindow->show();

}

@

So now I am getting errors like these upon changing namespace to DMM:

/home/pragati/MultiFuncTester/Components/Start/Build/../Source/Start.cpp:-1: In constructor 'Start::Startup::Startup()':

/home/pragati/MultiFuncTester/Components/Start/Build/../Source/Start.cpp:12: error: cannot convert 'DMM::DMMMenu' to 'Ui::DMMMenu*' in assignment*

2./home/pragati/MultiFuncTester/Components/Start/Build/../Source/Start.cpp:35: error: invalid use of incomplete type 'struct Ui::DMMMenu'

3./home/pragati/MultiFuncTester/Components/Start/Build/../../DMM/Include/DMM.h:9: error: forward declaration of 'struct Ui::DMMMenu'

r3willia

That's good - it means the compiler's got past the problem you were having before - now you've got the problem that you're using the wrong type for your member of Start::Startup.

I expect you want Start::Startup's declaration to read:

@class Startup : public QObject
{
Q_OBJECT

public:
Startup();
virtual ~Startup();
void GuiInit();

private:

DMM::DMMMenu *MainWindow;

};@

DMM::DMMMenu has a Ui::DMMMenu, but DMM::DMMMenu is not a Ui::DMMMenu (to use Object-orientated is-a / has-a terminology).

pragati

:(

I used it already before but as soon as I do this:
@DMM::DMMMenu *MainWindow;
@
I get error that
1./home/pragati/MultiFuncTester/Components/Start/Build/../../Start/Include/Start.h:27: error: 'DMM' does not name a type

and

2./home/pragati/MultiFuncTester/Components/Start/Build/../Source/Start.cpp:35: error: 'MainWindow' was not declared in this scope

r3willia

You're referencing DMM from within the namespace Start; it's possible you may have to be specific i.e. declare the parameter:
@::DMM::DMMMenu *MainWindow;@

Also make certain that "../../DMM/Include/DMM.h" does indeed define DMM::DMMMenu.

pragati

r3Willia,

I am still getting errors but not regarding this....anyways thank you so much...you came when I was not getting help from anyone....Thank you so much....wish I cud have personally thanked you...bt anyways....all the best and again ty....

pragati

hi...

Everything is working fine until when I write in main. In main I included one of the subdirectory's .h file and wrote some function like this I am posting here both the codes of main and that directory....

Error I am getting is :

/home/pragati/MultiFuncTester/Components/Main/Source/Main.cpp:-1: error: undefined reference to `Start::Startup::Startup()'

/home/pragati/MultiFuncTester/Components/Main/Source/Main.cpp:-1: error: undefined reference to `Start::Startup::GuiInit()'
/home/pragati/MultiFuncTester/Components/Main/Source

/Main.cpp:-1: error: undefined reference to `Start::Startup::~Startup()'

Similiar error for GuiInit....

Start.h

@
#ifndef START_H
#define START_H

#include "../../DMM/Include/DMM.h"

/****************************************************************************/
/**

\brief This class handles the initialization of the user interface.
/
/***************************************************************************/
namespace Start {

class Startup : public QObject
{
Q_OBJECT

public:

Startup();
virtual ~Startup();
void GuiInit();

private:

DMM::DMMMenu *MainWindow;

};

}

#endif // START_H

@

Start.cpp

@

#include "../../Start/Include/Start.h"
namespace Start {

Startup::Startup() : QObject()
{

// // GUI components

MainWindow = new DMM::DMMMenu();

}

/***************************************************************************/
/!

\brief Initializes the user interface
/
/***************************************************************************/
void Startup::GuiInit()
{
MainWindow->show();

}

}
@

Main.cpp

@
#include "../../Start/Include/Start.h"
#include <QApplication>
#include <QtGui>

int main(int argc, char *argv[])

{
QApplication app(argc, argv);
Start::Startup start;
start.GuiInit();
return app.exec();
}

@