How to get a class pointer without messing up data.

[Basti46]

Hello guys, my question is how can i use the same class pointer (or is it called instance?) in two different classes. I have a SettingsDialog class, where i set the values for my serial port, then i have the serial port class, where i use these values to configure the serial port. Then in the mainwindow i'll handle the settings widget, e.g. open the window etc.. But using something like

SettingsDialog p =new SettingsDialog(),  

in both classes (Serialport.c and MainWindow.c) seems to mess up something because the serialport won't open from time to time. I started to delete the settings pointer in the mainwindow, so i only have the settings in my serialPort.c. But is there a way to use the same object in two classes. I tried to give the pointer of the settings to my mainWindow:

SettingsDialog* SerialPort::getSettings()
{
    return this->settings;
}

But then again, i have to use something like

Serialport p =new Serialport();

To get the serialport, which could mess up something different (because i already did this in another class). Can anyone help me getting this problem solved because i don't fully understand how this works. Thank you

Thank you

[mrjj]

@Basti46 said:

Hi
To use the same instance of a class ,
in another class, you can simply
give it the pointer.
You can have SerialPort in main window and then give it to settings dialog;

so i if you have
SerialPort *MySerialPort; in the class in mainwindow .h

and create new instance for it.
MySerialPort = new SerialPort;

Then you can do
SettingsDialog p =new SettingsDialog(MySerialPort),

and give it directly in constructor
or u can make a setFunktion
SettingsDialog p =new SettingsDialog(),
p->setComPort(MySerialPort);

[Basti46]

@mrjj Thank you for your answer. Unfortunately I don't understand your answer and everything i tried did'nt work. Soo to make things clear, here is a code:

//HEADER MainWindow:
class SettingsDialog;

class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
.....
some functions...
......
private:
SettingsDialog *settings;
//SOURCE MainWindow
#include "MainWindow.h"
#include "ui_MainWindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow),
//----------here is the problem----------------------------------------------!
      settings(new SettingsDialog()),
//---------------------------------------------------------------------------------!
{
    ui->setupUi(this);
}
MainWindow::~MainWindow()
{
    delete settings;
    delete ui;
}
//just an example
void MainWindow::closeEvent(QCloseEvent *event)
{
        if (settings->isVisible())
    {
        settings->close();
    }
}
//HEADDER Serialport
class SerialPort : public QObject
{
    Q_OBJECT
....
//some more stoff
.....
private:
    SettingsDialog *settings;    
    QSerialPort *serialPort;               
    
//SOURCE Serialport
#include "SettingsDialog.h"
SerialPort::SerialPort(QObject *parent)
    : QObject(parent),
//----------------------------here is the problem------------------------!!
      settings(new SettingsDialog()),
//---------------------------------------------------------------------------------!!
{
}
//example function
void SerialPort::openSerialPort()
{
    SettingsDialog::Settings p = settings->settings();
    serialPort->setPortName(p.name);
}

Maybe you already answerd my question but i didn't see it yet.

[mrjj]

Hi
Just a note first
Having
class SerialPort : public QObject
and then
QSerialPort *serialPort;
Where only diffence is capital S to the main class is just confusing.

anyway, why is the issue with
settings(new SettingsDialog()),

did you declare it as
void settings(SettingsDialog *mydialog)

Im not sure what you dont understand.

To use a pointer to a class in another class, you simply give the pointer to the other class and it can use it

class B {};

class A {
  B* mykeptBpointer;
  setB(B* myb) {
    mykeptBpointer = myb;
  }
  void DoB {
    mykeptBpointer->xxxx();
  };

  A mya;
  B* myb = new B;
  mya.setB(b);

oh, is
settings(new SettingsDialog())
rather
settings = new SettingsDialog();