Transmitting data between classes - c++

Question

My code is set up in this way: the main window with a QTableWidget, and a control panel created with a different class from the MainWindow. In the control panel control there is a QListWidget where I want to load the titles of the header from the table, but being QTableWidget private, how can I pass data between the two classes?
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include "QControlPanel.h"
#include <QMainWindow>
#include <QWidget>
#include <QtGui>
#include <QTableWidget>
namespace Ui {
class MainWindow;
class GenerateXML;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
private:
Ui::MainWindow *ui;
QTableWidget* m_pTableWidget;
QControlPanel* preferences;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
this->setWindowIcon(QIcon("DrawItem.ico"));
this->setWindowTitle("DrawItem");
resize(890, 475);
m_pTableWidget = new QTableWidget(this);
m_TableHeader<<"A"<<"B"<<"C"<<"D"<<"E";
m_pTableWidget->setHorizontalHeaderLabels(m_TableHeader);
m_pTableWidget->resizeColumnsToContents();
m_pTableWidget->verticalHeader()->setVisible(false);
m_pTableWidget->move(30, 75);
m_pTableWidget->resize(410, 151);
preferences = new QControlPanel(this);
}
QControlPanel.h
#include <QDialog>
#include <QTableWidget>
#ifndef QCONTROLPANEL_H
#define QCONTROLPANEL_H
class QControlPanel : public QDialog
{
Q_OBJECT
public:
explicit QControlPanel(QWidget *parent = 0);
~QControlPanel();
public slots:
void customHeader(QTableWidget *table);
private:
QListWidget *headerlist;
private slots:
};
#endif
QControlPanel.cpp
#include "QControlPanel.h"
QControlPanel::QControlPanel(QWidget *parent) :
QDialog(parent)
{
headerlist = new QListWidget(inputHeader);
headerlist->setGeometry(140, 15, 140, 130);
}

Answer 1

You can have a signal in the QControlPanel class which retrieves the headers. So QControlPanel can be like :
class QControlPanel : public QDialog
{
Q_OBJECT
public:
explicit QControlPanel(QWidget *parent = 0);
~QControlPanel();
signals:
QStringList getHeaders();
private:
QListWidget *headerlist;
};
And connect the getHeaders() signal to a slot of the class which contains the list of columns to retrieve them. This should be done in the constructor of the MainWindow :
connect(preferences,SIGNAL(getHeaders()),this,SLOT(getTableHeader()));
getTableHeader() is a slot in MainWindow which return the header columns :
QStringList getTableHeader()
{
return m_TableHeader;
}
Now you can access the headers in QControlPanel :
QControlPanel::QControlPanel(QWidget *parent) :
QDialog(parent)
{
headerlist = new QListWidget();
headerlist->insertItems(0, getHeaders());
}