Using Qthread to run a function - c++

Question

I want to run a function of a class as a thread continuously,till the object of the class is destroyed.
client.h
class client:public QWidget
{
Q_OBJECT
public:
//some declarations
client();
void setclientui();
//some ui elements
void receiveme(); //i want this function to be run as a thread
//It has to be run continuously to receive
//messages from socket and when a message is
//received ,it must display it in the gui.
public slots:
int prework();
void sendme();
};
Note:receiveme() uses recv() of tcp sockets which gets blocked until message is received.
client.cpp
void receiveme(){
while(1){
if(recv(sockfd,receivebuf,1024,0)<0)
{
qDebug()<<errno;
break;
}
receivebuf[20]='\0';
qDebug()<<receivebuf;
outputbox->append(a);
}}
mainwindow.h
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
Dialog* newdialog;//join a new chat
QString ipp,portt;
QTabWidget *wdg;
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void receivesocketaddress();
void on_actionJoin_a_chat_triggered();
};
mainwindow.cpp
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
wdg=new QTabWidget;
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_actionJoin_a_chat_triggered()
{
newdialog=new Dialog();
newdialog->setWindowTitle("Join a chat");
newdialog->setModal(true);
qDebug()<< QObject::connect(newdialog->conne,SIGNAL(clicked()),this,SLOT(receivesocketaddress()));
newdialog->exec();
}
void MainWindow::receivesocketaddress()
{
client *aclient=new client;
aclient->iptoconnect=newdialog->ip->text().toLocal8Bit().data();
aclient->porti=newdialog->port->text().toLocal8Bit().data();
if(aclient->prework()==0)//ie connected
{
newdialog->close();
wdg->addTab(aclient,tr("new chat"));
setCentralWidget(wdg);
//here the ui is shown.Now the aclient->receiveme() should
//running
}
else
{
newdialog->displayerror();
layout->addWidget(error,3,0,2,2);
qDebug()<<"cud not connect";
}
}
If aclient->prework()==0 then a gui is displayed but how can i run aclient->receiveme() at this time as a thread so that it is continuously running and reading messages from socket.If a message is received,it should be displayed in the gui.
Without thread the gui would freeze.I tried to use QThread::movetothread() but i receive the following error
QThread::cannot move object with parent
and to use subclass method, client class must inherit QThread but since it is already inheriting QWidget,the following error is thrown
call to QObject is ambiguous
How can i use QThread here?

Answer 1

Widgets can run only within GUI thread, so you need to implement client as QObject subclass and communicate with UI via signal/slot connection. Qt wont allow you to do outputbox->append(a) in non UI thread (Supposing that outputbox is some QWidget here);
You probably don't even need to use threads here - Qt provides it's own socket classes with event (signal/slot) based API;
If you still need to use recv() in different thread, you need to subclass QThread (one approach) or QObject (another approach); In both cases you need to have signal like messageReceived(QByteArray) that will be connected to slot in your UI object that will handle message; So receiveme() slot might looks like:
void client::receiveme()
{
while(1){
if(recv(sockfd,receivebuf,1024,0)<0)
{
qDebug()<<errno;
break;
}
receivebuf[20]='\0';
QByteArray msg(receivebuf);
emit messageReceived(msg);
}
}
This article might help