[Moved] Document/View application

? Offline

Thanks, I'll give it a try.

giesbert

Hi mlong,

I think you meant:

MainWindow.cpp:
@
MainWindow::someMethod() {
userEntry->userdata(&info); // Pass the address of info.
// or
userEntry->userdata(info); // using reference
}
@

as userEntry is a pointer to the UserEntry class...

andre

Note that you might want to use forward declares in headers instead of includes. That means:

@
//MainWindow.h
struct Information;

//...
private:
Information* m_information;
@

and then only in the MainWindow.cpp do the #include of Information.h.

It makes compilation faster.

? Offline

No luck - below is the MainWindow and Information code. I left out the UserData code to see if this would work before making it any more complex. This generates a compile error code:

         request for member 'a' in 'info', which is of non-class type 'Information*'

Is this caused by a syntax error that I am missing?

MainWindow.h
@
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

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

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

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

private:
struct information *info;

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);

info = new information;

info.a = "A";
info.b = "B";
info.c = "C";

}

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

Information.h
@
#ifndef INFORMATION_H
#define INFORMATION_H

#include <QtGui>

struct information
{
QString a;
QString b;
QString c;
};

#endif // INFORMATION_H

@

Added @ tags around code sections. Please do that yourself next time; Andre

andre

There seems to be some weird mismatch of #ifdefs and #endif's in your code. Perhaps you should fix these first?

Oh, and in your MainWindow, you have a pointer to an Information instance, while you do not seem to be creating an instance and trying to assign to it as if it is a normal member variable.

? Offline

That seems to have come from copying and pasting. The definitions are okay in my files.

andre

[quote author="CapnMikey" date="1315495836"]That seems to have come from copying and pasting. The definitions are okay in my files.[/quote]
Then please update your previous post to reflect the actual state of your code.

? Offline

Line 15 in Information.h should be line 25 in MainWindow.h. Sorry about the mixup.

andre

[quote author="CapnMikey" date="1315496093"]Line 15 in Information.h should be line 25 in MainWindow.h. Sorry about the mixup.[/quote]
Please just use the Edit button next to your post to modify it and fix the mixup.

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Okay, the code above has been modified.

Thanks for pointing out the edit button.

giesbert

Your struct is named information, but the definition in mainwindow.h is Information. C++ is case sensitive...

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I corrected the case error as well (see post above). I still get the same error message.

andre

Did you also note the remark I posted above?

[quote author="Andre" date="1315495737"]Oh, and in your MainWindow, you have a pointer to an Information instance, while you do not seem to be creating an instance and trying to assign to it as if it is a normal member variable. [/quote]

? Offline

I added line 13 to the MainWindow.cpp above, but I still get the same error message. Is this what you are referring to?

andre

Either, change line 20 in MainWindow.h to
@
Information info;
@
and remove line 13 from MainWindow.cpp, or

change line 20 in MainWindow.h to
@
Information* info;
@
and change lines 15-17 in MainWindow.cpp into:
@
info->a = "A";
info->b = "B";
info->c = "C";
@
and insert this line as line 24:
@
delete info;
@

In either case, get yourself a good book on C++ to get yourself a solid introduction into the language you are working with. Qt does not shield you from having to learn C++.

? Offline

Andre (and everyone else)-

Thanks for your help. The first option compiled correctly. Having seen something that works I hope I can figure it out from here.

Your last suggestion is appropriate. However, I have a large stack of books on C++ programming. The problem is the definition of the word "good". I learned chemical thermodynamics by using a large stack of textbooks. None of them were particulary good. But, where one authors explanation failed another author provided a more thorough explanation. I was able to piece it together that way. I haven't found that approach to work well for understanding C++.