error building a window application

[russjohn834]

Hi,

I'm stuck at debugging an issue.

I have two windows StageOneMain and ClinicalProtocolWindow

I want to open ClinicalProtocolWindow from StageOneMain and go back.

On StageOneMain I did the following:

#ifndef STAGEONEMAIN_H
#define STAGEONEMAIN_H

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


QT_BEGIN_NAMESPACE
namespace Ui { class StageOneMain; }
QT_END_NAMESPACE

class StageOneMain : public QMainWindow
{
    Q_OBJECT

public:
     StageOneMain(QString, QWidget *parent = nullptr);
    ~StageOneMain();
     ClinicalProtocolWindow *clinwindow;
     QString pLabel;
private:
    Ui::StageOneMain *ui;
};
#endif // STAGEONEMAIN_H

.cpp

void StageOneMain::on_pushButton_programs_clicked()
{

    this->close();
    clinwindow = new  ClinicalProtocolWindow(pLabel, nullptr);
    clinwindow -> setAttribute(Qt::WA_DeleteOnClose);
    clinwindow -> show();

}

and ClinicalProtocolWindow as follows:

#ifndef CLINICALPROTOCOLWINDOW_H
#define CLINICALPROTOCOLWINDOW_H

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

namespace Ui {
class ClinicalProtocolWindow;
}

class ClinicalProtocolWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit ClinicalProtocolWindow(QString, QWidget *parent = nullptr);
    ~ClinicalProtocolWindow();
    QString pLabel;

private slots:
    void on_pushButton_clicked();

private:
    Ui::ClinicalProtocolWindow *ui;
};

#endif // CLINICALPROTOCOLWINDOW_H

and .cpp

#include "clinicalprotocolwindow.h"
#include "ui_clinicalprotocolwindow.h"

ClinicalProtocolWindow::ClinicalProtocolWindow(QString patientLabel, QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::ClinicalProtocolWindow)
{
    ui->setupUi(this);
    pLabel = patientLabel;
}

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

void ClinicalProtocolWindow::on_pushButton_clicked()
{

}

I get the errors pointing below

     ClinicalProtocolWindow *clinwindow;

and the errors are:

stageonemain.h:33: error: C2143: syntax error: missing ';' before '*'
stageonemain.h:33: error: C4430: missing type specifier - int assumed. Note: C++ does not support default-int
stageonemain.h:33: error: C2238: unexpected token(s) preceding ';'

It seems that I have overlooked something. I'm feeling frustrated and stuck on this problem.

Can you spot any issues here?

Thanks

[JoeCFD]

@russjohn834 your posted header file is not complete.

[russjohn834]

@JoeCFD Hi, thanks. I just modified it

[JoeCFD]

@russjohn834 no line 33. Better to make variables private.

#ifndef STAGEONEMAIN_H
#define STAGEONEMAIN_H

#include <QMainWindow>

QT_BEGIN_NAMESPACE
namespace Ui { class StageOneMain; }
QT_END_NAMESPACE

class ClinicalProtocolWindow;

class StageOneMain : public QMainWindow
{
    Q_OBJECT

public:
     StageOneMain(QString, QWidget *parent = nullptr);
    ~StageOneMain();

private:
    Ui::StageOneMain *ui{};     

    ClinicalProtocolWindow *clinwindow{};
    QString pLabel;
};
#endif // STAGEONEMAIN_H

[JonB]

@russjohn834
You have two .h files, each trying to include the other. Each has a "guard".

#ifndef STAGEONEMAIN_H
#define STAGEONEMAIN_H

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

and

#ifndef CLINICALPROTOCOLWINDOW_H
#define CLINICALPROTOCOLWINDOW_H

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

Follow through in your head/on a piece of paper what happens. You will find that when

 ClinicalProtocolWindow *clinwindow;

in StageOneMain.h is reached ClinicalProtocolWindow class is not defined. Hence the error messages.

Mutual inclusion like this is often a sign a bad design. I suspect it is here. Why should both of these classes need to know al about each other just because you have two windows opening?

Find a way to get round this. Just having StageOneMain.h go class ClinicalProtocolWindow; like that may be enough to break to the dependency/error. Or as it currently stands ClinicalProtocolWindow has no need to include StageOneMain.h.

[russjohn834]

@JoeCFD said in error building a window application:

@russjohn834 no line 33.

I modified the original .h file to show only what I thought would be relevant.
It looks like something silly I'm doing!
What is strange is , I have other windows works fine. The error is only when I added the new ClinicalProtocolWindow

[JonB]

@russjohn834
If you read my answer it will tell you why.
And if you look at @JoeCFD's code you will see he has inserted

class ClinicalProtocolWindow;

and removed #include "clinicalprotocolwindow.h". Which will make it compilable.

[JoeCFD]

@russjohn834 as JonB pointed out, you have mutual include in these two header files. Use changes I made in your header and you will be good. Add include header in .cpp files.

[Pl45m4]

Few things in addition to the circular inclusion/dependency you did with your two classes :

@russjohn834 said in error building a window application:

class ClinicalProtocolWindow : public QMainWindow

I wouldn't make ClinicalProtocolWindow a QMainWindow-based class unless you really need the toolbars and menus, which come with it.
QWidget or even QDialog is better, esp. since you have Qt::WA_DeleteOnClose set.
For example, create your dialog, fill in/change whatever you want to edit and return to your mainWindow again.
(I assume it's gonna be some patient form)

@russjohn834 said in error building a window application:

this->close();
clinwindow = new ClinicalProtocolWindow(pLabel, nullptr);
clinwindow -> setAttribute(Qt::WA_DeleteOnClose);
clinwindow -> show();

This could easily run into QApplication:quitOnLastWindowClosed when there are no other windows or parent widgets involved and then your app just exits without showing anything.

• https://doc.qt.io/qt-6/qguiapplication.html#quitOnLastWindowClosed-prop

Make sure you have a parent window or change the order of close() / hide() and show()

[russjohn834]

@Pl45m4 , @JonB , @JoeCFD Many thanks for your feedback :)