How to initialize a QProcess in the following windows

[Santosh Reddy]

Then you could share the same instance of QProceess between them, or let one of the window own the QProcess and then and expose a function to write to the QProcess.

BTW, what was your original problem, writing to QProcess, use QProcess.write() (assuming the process talks on stdin)

[Max Fleischer]

I would rather share the same instance of QProcess between the windows, how can I do that?

At first I tried to write to the process from control_window, but the UI crashed because the process wasn't initialized.

control window header:

#ifndef CONTROL_WINDOW_H
#define CONTROL_WINDOW_H
 
#include <QMainWindow>
#include <QProcess>
 
namespace Ui {
class control_window;
}
 
class control_window : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit control_window(QWidget *parent = 0);
    ~control_window();
 
private slots:
    void on_control_window_Back_clicked();
 
private:
    Ui::control_window *ui;
 
    QProcess *m_opc_ua_server;
};
 
#endif // CONTROL_WINDOW_H

#ifndef CONTROL_WINDOW_H
#define CONTROL_WINDOW_H

#include <QMainWindow>
#include <QProcess>

namespace Ui {
class control_window;
}

class control_window : public QMainWindow
{
    Q_OBJECT

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

private slots:
    void on_control_window_Back_clicked();

private:
    Ui::control_window *ui;

    QProcess *m_opc_ua_server;
};

#endif // CONTROL_WINDOW_H

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control window source:

#include "control_window.h"
#include "configuration_window.h"
#include "ui_control_window.h"
 
control_window::control_window(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::control_window)
{
    ui->setupUi(this);
}
 
control_window::~control_window()
{
    delete ui;
}
 
void control_window::on_control_window_Back_clicked()
{
    m_opc_ua_server->write("j\n");
}

#include "control_window.h"
#include "configuration_window.h"
#include "ui_control_window.h"

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

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

void control_window::on_control_window_Back_clicked()
{
    m_opc_ua_server->write("j\n");
}

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Besides how can I check the Process State? It enters this if regardless whether the process is running or not.

if (m_opc_ua_server->Running)
    {
 
    }

if (m_opc_ua_server->Running)
    {

    }

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[jefftee]

Try m_opc_ua_server->state() == QProcess::Running instead.

[Max Fleischer]

Thanks, that's working.

[jefftee]

Great, also, to "share" the QProcess with other classes, either pass the QProcess pointer to the other class' constructor or create a getter method in the class that creates/owns the QProcess, for example:

QProcess* control_window::get_process()
{
    return m_opc_ua_server;
}

QProcess* control_window::get_process()
{
    return m_opc_ua_server;
}

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[Max Fleischer]

How can I pass the QProcess Pointer to the constructor?
I tried to use a getter function but the UI still crashes when I write to the process from control_window. I've put the getter function in the header of configuration_window.

configuartion window header:

#ifndef CONFIGURATION_WINDOW_H
#define CONFIGURATION_WINDOW_H
 
#include <QMainWindow>
#include <QProcess>
 
class version_selection;
class control_window;
 
namespace Ui {
class configuration_window;
}
 
class configuration_window : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit configuration_window(QWidget *parent = 0);
    ~configuration_window();
 
    void send_input_to_server();
 
    QProcess *get_process()
    {
        return m_opc_ua_server;
    }
    void set_process(QProcess *server)
    {
        m_opc_ua_server = server;
    }
 
private slots:
    void on_configuration_window_Exit_clicked();
 
    void on_configuration_window_Back_clicked();
 
    void on_configuration_window_Start_clicked();
 
private:
    Ui::configuration_window *ui;
 
    version_selection *m_version_selection;
 
    control_window *m_control_window;
 
    QProcess *m_opc_ua_server;
};
 
#endif // CONFIGURATION_WINDOW_H

#ifndef CONFIGURATION_WINDOW_H
#define CONFIGURATION_WINDOW_H

#include <QMainWindow>
#include <QProcess>

class version_selection;
class control_window;

namespace Ui {
class configuration_window;
}

class configuration_window : public QMainWindow
{
    Q_OBJECT

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

    void send_input_to_server();

    QProcess *get_process()
    {
        return m_opc_ua_server;
    }
    void set_process(QProcess *server)
    {
        m_opc_ua_server = server;
    }

private slots:
    void on_configuration_window_Exit_clicked();

    void on_configuration_window_Back_clicked();

    void on_configuration_window_Start_clicked();

private:
    Ui::configuration_window *ui;

    version_selection *m_version_selection;

    control_window *m_control_window;

    QProcess *m_opc_ua_server;
};

#endif // CONFIGURATION_WINDOW_H

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