How to read struct members from another class

rezaMSLM

I have a struct in my mainwindow class:

#ifndef MAINWINDOW_H
    #define MAINWINDOW_H

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

    namespace Ui {
      class MainWindow;
    }

    class MainWindow : public QMainWindow
    {
      Q_OBJECT
  
      public:
        explicit MainWindow(QWidget *parent = 0);
        ~MainWindow();
    
        struct properties{
          int ID = -1;
        };

        properties ret_func();
      private slots:
        void on_btn1_clicked();

      private:
        Ui::MainWindow *ui;
        properties _properties;
        Dialog *_dialog;
    };

    #endif // MAINWINDOW_H

I set value to it's memeber in mainwindow.cpp by clicking on btn1:

  MainWindow::properties MainWindow::ret_func()
    {
      return _properties;
    }

    void MainWindow::on_btn1_clicked()
    {
      _properties.ID = ui->lineEdit->text().toInt();
      qDebug()<<_properties.ID;
      _dialog->exec();
    }

by clicking on btn1 another window is opened and I want to read the struct member value by clicking on btn2. This is my code:

 void Dialog::on_btn2_clicked()
    {
        qDebug()<<MainWindow::ret_func().ID;//->this line has error
    }

Error:

    error: cannot call member function 'MainWindow::properties 
    MainWindow::ret_func()' without object
     qDebug()<<MainWindow::ret_func().ID;
                                    ^

I have read some threads having similar problems but couldn't understand solution
please help me

mrjj

Hi
you need a pointer to the existing MainWindow and
say
qDebug()<< winPtr->ret_func().ID;

However, since Dialog also needs _properties, why not give it to Dialog directly
by extending the constructor to take such parameter.
Dialog mydia(this, _properties );
mydia.exec();

rezaMSLM

@mrjj
you mean this?

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

Error:

error: no matching function for call to 'Dialog::Dialog(MainWindow*, MainWindow::properties&)'
     _dialog = new Dialog(this, _properties);
                                           ^

mrjj

@rezaMSLM
yes but you have to change the Dialogs constructor so it can take one.

rezaMSLM

@mrjj
I don't get your meaning

mrjj

@rezaMSLM
Show Dialogs constructor please :)

rezaMSLM

@mrjj

public:
    explicit Dialog(QWidget *parent = 0);

:D

mrjj

@rezaMSLM
#include "MainWindow.h" // so it knows it.

explicit Dialog(QWidget *parent , MainWindow::properties & theProps );

also add the same in . cpp file

Note the &. if you omit that, it will get a copy.

rezaMSLM

@mrjj
in my dialog.h:

public:
    explicit Dialog(QWidget *parent = 0, MainWindow::_properties & theProps);
    ~Dialog();

in dialog.cpp

Dialog::Dialog(QWidget *parent, MainWindow::_properties &theProps) :
    QDialog(parent),
    ui(new Ui::Dialog)
{
    ui->setupUi(this);
}

But I receive Errors in these lines of mainwindow.h:

private:
    Ui::MainWindow *ui;
    properties _properties;// error: 'MainWindow::properties MainWindow::_properties' is private
     properties _properties;
                ^
    Dialog *_dialog;// error: 'Dialog' does not name a type Dialog *_dialog;
};

and in dialog.h:

public:
    explicit Dialog(QWidget *parent = 0, MainWindow::_properties & theProps);/* error: default argument missing for parameter 2 of 'Dialog::Dialog(QWidget*, int&)'
     explicit Dialog(QWidget *parent = 0, MainWindow::_properties & theProps);
              ^
*/
    ~Dialog();

mrjj

Hi
Remove the =0
explicit Dialog(QWidget *parent = 0, MainWindow::_properties & theProps);
or swap the order of parameters if you want a default value.

for the
Dialog *_dialog;// error: 'Dialog' does not name a type Dialog *_dialog;

is due to us using Mainwindow.h in Dialog.h and made a circular includes. ( which is forbidden)

to fix it.
over MainWindow class.
type
class Dialog; // this is a forward
and move the #include "Dialog.h" to mainwindow. cpp file.