pass data from one class to another qt

Question

I want to pass data from one form to another. I did some research and I found out how to do it, but my code doesn't work!!
Here is my code:

MainWindow.h

signals:
    void signalEmission(const String &port) ;

MainWindow.cpp

void MainWindow::on_pushButtonclicked()
{

   emit signalEmission(nameArea->toPlainText()) ;

}

class.h

private slots:
  void mySlot(const QString &port) ;

class.cpp

void class::mySlot(const QString &port)
{
   messages->append(port) ;
}

main.cpp

  MainWindow h ;
    class c;

 QObject::connect(&h,SIGNAL(signalEmission(const QString&)),&c,SLOT(research(const QString&))) ;

I don't get the port number from the MainWindow class!! Can someone please help.

---

EDIT: Here is my code

history.h

#ifndef HISTORY_H
#define HISTORY_H

#include <QMainWindow>
#include <ui_history.h>
#include <QTcpSocket>

class History : public QMainWindow, private Ui::History
{
    Q_OBJECT

public:
    explicit History();

private slots:
    void on_searchButton_clicked();
signals:
        void signalEmission( QString port) ;

};

#endif // HISTORY_H

history.cpp

#include "history.h"
#include "ui_history.h"
#include "client.h"
#include "ui_client.h"
#include <QDebug>
#include <QtNetwork>

History::History() {

    setupUi(this);
    resize(500,200);
    move(300,300) ;

}


void History::on_searchButton_clicked()
{

   emit this->signalEmission(receiverPort->toPlainText()) ;

   this->close() ;
}

client.h

#ifndef HEADER_CLIENT
#define HEADER_CLIENT

#include <QMainWindow>
#include <QtWidgets>
#include <QtNetwork>
#include <QSqlDatabase>
#include "history.h"
#include "ui_client.h"

class client : public QMainWindow, private Ui::client
{
    Q_OBJECT

    public:
    explicit client();

    public slots:
        void on_connexionButton_clicked();
        void on_sendButton_clicked();
        void receivedData();
        void connectClient();
        void disconnect();
        void socketError(QAbstractSocket::SocketError erreur);

        void on_disconnexionButton_clicked();
        void on_connectedClientsButton_clicked();
        void on_refreshButton_clicked();

        void on_historyButton_clicked();
        void research( QString port) ;




private slots:
        void on_clearButton_clicked();

        void on_connectedList_pressed();

private:
        QTcpSocket *socket; // Représente le serveur
        quint16 messageLength;

        History *his;
        QSqlDatabase db ;
        QStringList *cc ;
        QStringListModel *ccl ;
        QString selectedTexts ;


};

#endif

client.cpp

#include "client.h"
#include "history.h"
#include "ui_history.h"
#include "ui_client.h"
#include <QMainWindow>
#include <QSqlDatabase>
#include <QSqlError>
#include <QSqlQuery>
#include <QDebug>

client::client()
{
      setupUi(this);

      cc = new QStringList();
      ccl = new QStringListModel() ;


      socket = new QTcpSocket(this);
      connect(socket, SIGNAL(readyRead()), this, SLOT(receivedData()));
      connect(socket, SIGNAL(connected()), this, SLOT(connectClient()));
      connect(socket, SIGNAL(disconnected()), this, SLOT(disconnect()));
      connect(socket, SIGNAL(error(QAbstractSocket::SocketError)), this, SLOT(socketError(QAbstractSocket::SocketError)));

      messageLength = 0;

      disconnexionButton->setEnabled(false);
      connectedClientsButton->setEnabled(false);
      sendButton->setEnabled(false);
      clearButton->setEnabled(false);
      refreshButton->setEnabled(false);
      historyButton->setEnabled(false);
}

void client::research(QString port){


    qDebug() << port ;


    //messagesList->cleanHistory() ;
   /* QSqlQuery qry(db);
    qry.prepare("SELECT * FROM conversations where sender=? and receiver=?");
    qry.addBindValue(socket->localPort()) ;
    qry.addBindValue(port) ;
    if(!qry.exec()){
       qDebug() << "Problem with Select conversation" ;
    }
    else{
        qDebug() << "Select conversation query executed successfully" ;
    }

    messagesList->append(tr("<strong>Historique des conversations:</strong>")) ;
   while(qry.next())
      {
       messagesList->append(qry.value(2).toString()+"  "+qry.value(3).toString()) ;
      }*/


}

Can someone please tell me what's wrong. It's driving me crazy!!

Answer 1

There are so many little issues here, looking at the comments, this code does not appear to be the real code anyway...? it is better to post the real code then to send some very buggy example - it will confuse people trying to help you.

Anyway, a few things to try to help you:

1. Is your class "class" really called "class"?, this is a key word already, so I would rename that, I have no idea what the compiler will make of that :o
2. Make sure all the function signatures are identical for your slots and signals, i.e. they all take "const QString &".
3. Check the connection return value is true (ok) and not false (failed): if (!QObject::connect(...)) {printf("Connection failed!\n");}. If its false then something is wrong.
4. Try a simple start-point, i.e. make a slot and signal that take a QString such that: void MainWindow::on_pushButtonclicked() { emit signalEmission((QString) "test"); }

finally, please show any errors/warnings from compilation and from debug output.