Passing data between MainWindow and my class

[r2com]

So I have a simple class with one variable called param1, constructor, and two functions to set/get that parameter:

So here are the sources of ctester.h and ctester.cpp

#ifndef CTESTER_H
#define CTESTER_H
 
 
class CTester {
 
public:
    CTester();	// constructor
    void SetParam1(int value);
    int GetParam1(void);
 
private:
    int param1;
 
};
 
#endif // CTESTER_H

#ifndef CTESTER_H
#define CTESTER_H


class CTester {

public:
    CTester();	// constructor
    void SetParam1(int value);
    int GetParam1(void);

private:
    int param1;

};

#endif // CTESTER_H

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CTester::CTester(void)
{
    // initializing all the parameters
    param1 = 0;
}
 
void CTester::SetParam1(int value)
{
    param1 = value;
}
 
int CTester::GetParam1(void)
{
    return param1;
}

CTester::CTester(void)
{
    // initializing all the parameters
    param1 = 0;
}

void CTester::SetParam1(int value)
{
    param1 = value;
}

int CTester::GetParam1(void)
{
    return param1;
}

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My main.cpp and mainwindow.cpp files are rather simple, since I just started a QMainWindow application in QtCreator:

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

#include "mainwindow.h"
#include <QApplication>


int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

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#include "mainwindow.h"
#include "ui_mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}
 
MainWindow::~MainWindow()
{
    delete ui;
}

#include "mainwindow.h"
#include "ui_mainwindow.h"

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

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

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What I am not quite sure is, what is the most proper way of getting/setting that param1 variable in my class through that MainWindow form?
The search on QtCentre gives tons of similar threads BUT about sharing data between dialogs or dialogs and main window, but I did not see any description in docs or the forum threads about reading/writing to own class.

In other words, I have my Qt GUI interface, but what I want to achieve now is create now personal c++ class which is "tied" to that GUI and updated by it. I do have two buttons on the MainWindow form, Set and get, and the editbox for setting the value and label for showing the value of param1 when get button is clicked.

Keep in mind that I want to keep ctester.h and ctester.cpp as c++ source files only, i.e. no Qt related macros/keywords there.
Now, does it mean that I need another "intermediate" wrapper class for this mechanism to work? Or there is a better, more elegant approach to achieve what I just described?

[d_stranz]

So where does your instance of the CTester class live? Have you even declared an instance of it anywhere? If you haven't declared an instance of it, then how do you expect to call its Get and Set methods from any other class at all?

There is no magic to mixing pure C++ and Qt classes; the Qt libraries -are- C++ and the macros (like Q_OBJECT) are just aids to paste a lot of boilerplate code into header files and elsewhere. Signals and slots are just ordinary C++ methods and are called from within the Qt framework just like any other C++ method.

Of course, you have to have an instance of a class first before you can call any of its non-static members. Where do you want your instance of CTester to live?

[r2com]

I declared instance of CTester inside private section of QMainWindow:

private:
    Ui::MainWindow *ui;
    CTester aa;

private:
    Ui::MainWindow *ui;
    CTester aa;

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Then on the form designer I right click on the Get button and choose "GoTo SLot->clicked()" and enter this code:

void MainWindow::on_param1Get_clicked()
{
    aa.GetParam1();
    QString s = QString::number(aa.GetParam1());
    ui->param1Label->setText(s);
}

void MainWindow::on_param1Get_clicked()
{
    aa.GetParam1();
    QString s = QString::number(aa.GetParam1());
    ui->param1Label->setText(s);
}

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It does give me a LNK2019 error on compile.
And also, I have a feeling that I'm trying to achieve this in an ugly way and there gotta be an elegant solution.

[d_stranz]

LNK2019

And what else does it say besides "LNK2019"? Probably something about can't find a CTester constructor or a CTester:: GetParam() method, right? So did you add "Tester.cpp" or whatever you called the source file to the project? Did you add the paths to and names of your Qt library ".lib" files to the link properties? (Qt5Core, Qt5Gui, and Qt5Widgets, at a minimum for a GUI project).

By the way, you -do- realize that the code in your line 3 does nothing, right? Gets the parameter value, doesn't assign it to anything, then throws it away once the statment is done.

[anda_skoa]

And also, I have a feeling that I'm trying to achieve this in an ugly way and there gotta be an elegant solution.

Aside from the linker error and the unnecessary line that d_stranz mentioned this looks fine.

Cheers,
_