Qt slot is not activated - c++

Question

So i have 2 classes, one named ConsoleInput, which contains member function check4Flood and second named AntiFloodSys, in which connect function for signal-slot system is present, and also its signal (QTimer) and slot.
AntiFloodSys object is in check4Flood member function which scope never ends as inside there is infinite while loop. Thus the object is never destroyed. So when the object anti is created, the constuctor of AntiFloodSys class is called and therefore the connection between signal and slot.
My question at which point of the code the connection timeout signal and mySlot is separated, so the slot is never fired?
ConsoleInput cpp file looks like this:
void ConsoleInput::check4Flood(int& lineCounter)
{
AntiFloodSys anti;
while(1)
{
std::string chatLine[2];
std::cin >> chatLine[0] >> chatLine[1];
anti.input(chatLine[0], chatLine[1]);
}
}
and AntiFloodSys class like this:
AntiFloodSys::AntiFloodSys(QObject *parent) : QObject(parent)
{
timeFrame = 1000 ;
timer = new QTimer;
connect(timer, SIGNAL(timeout()), this, SLOT(mySlot()));
timer->start(timeFrame);
std::cout << "AntiFloodSys constructor - timer starts " << "\n";
}
AntiFloodSys::~AntiFloodSys()
{
std::cout << "AntiFloodSys Destructor" << "\n";
}
void AntiFloodSys::input(std::string nick_, std::string line_)
{
nick = nick_;
line = line_;
std::cout << "nick: " << nick << " line: " << line << " " << "\n";
}
void AntiFloodSys::mySlot()
{
std::cout << "slot" << "\n";
}

Answer 1

The problem is your while(1): the Qt event loop is never processed because your program is blocked in this loop.
You can force the event loop processing calling QCoreApplication::processEvents() but the std::cin is a blocking function. So, it will not completly solve your problem.
You should move your loop in a dedicated thread that will send data to the main thread (e.g. signals/slots system).
You can also use the QSocketNotifier class to create a non blocking stdin access.
A quick example:
class Widget: public QWidget
{
Q_OBJECT
public:
Widget(): QWidget(), input(new QLabel("Edit", this))
{
connect(this, &Widget::displayText, input, &QLabel::setText);
}
private:
QLabel* input;
signals:
void displayText(QString const&);
};
class UserInput: public QObject
{
Q_OBJECT
public:
UserInput(): QObject()
{}
public slots:
void run()
{
while(1) // User Input in an infinite loop
{
std::string line;
std::cin >> line;
emit inputReceived(QString::fromStdString(line));
}
}
signals:
void inputReceived(QString const&);
};
int main(int argc, char** argv) {
QApplication app(argc, argv);
Widget* w = new Widget();
UserInput* input = new UserInput();
QThread* thread = new QThread();
input->moveToThread(thread); // Move the user input in another thread
QObject::connect(thread, &QThread::started, input, &UserInput::run);
QObject::connect(input, &UserInput::inputReceived, w, &Widget::displayText);
thread->start();
w->show();
return app.exec();
}