Qt new thread are created every tick? - c++

Question

Why every tick of QTimer creates new thread? My application needs to run as long as possible, but after xx of ticks it freeze, it still running (it's responding), but next ticks are not executed. I looked into debug info and i saw:
QThread::start: Failed to create thread () QThread::start: Failed to
create thread () QThread::start: Failed to create thread ()
QThread::start: Failed to create thread () QThread::start: Failed to
create thread () QThread::start: Failed to create thread ()
QThread::start: Failed to create thread () QThread::start: Failed to
create thread ()
waat?
Tick are executed every xx seconds, signal is located into QWidged (which is a one of tab of TabWidget)
namespace Ui {
class accountTab;
}
class accountTab : public QMainWindow
{
Q_OBJECT
public:
explicit accountTab(QWidget *parent = 0);
class player *_player;
~accountTab();
private slots:
void on_clean_timer_clicked();
public:
Ui::accountTab *ui;
};
void accountTab::on_clean_timer_clicked()
{
if(user->timers.value("clean")->isActive()) {
_player->timers.value("clean")->stop();
}
else if(!user->timers.value("clean")->isActive()) {
_player->timers.value("clean")->start(1800000); //900000
}
}
_player is a simple class.
_player->clean() execute a few static classes, which are try/catched.
player.h
class player : public QObject
{
Q_OBJECT
public:
player();
~player();
player(Ui::accountTab *tab, std::string login, std::string password);
player(Ui::accountTab *tab, User user);
public:
bool logIn();
Ui::accountTab *tab = new Ui::accountTab();
public slots:
void clean();
private:
User user;
QMap<std::string, QTimer*> timers;
void initializeTimers();
};
player.cpp
player::player(Ui::accountTab *tab, std::string login, std::string password)
{
this->tab = tab;
this->user.login = login;
this->user.password = password;
}
player::~player()
{
delete this->manager;
delete this->tab;
}
bool player::logIn()
{
...
Log::writeLog("Login completed!", *this);
return true;
}
bool player::setup(bool saved, bool save)
{
if(!this->logIn())
return false;
Packets::sendPacket("getSimulation", *this);
this->initializeTimers();
return true;
}
void player::initializeTimers()
{
this->timers.insert("clean", new QTimer(this));
connect(this->timers.value("clean"), SIGNAL(timeout()), this, SLOT(cleanZoo()));
}
void player::clean()
{
Packets::sendPacket()
}
user class in player class keeps login and password.
timers is a QMap: QMap timers;
Packets::sendPacket() is static void
and sendPacket()
QString httpManager::sendPacket()
{
QNetworkRequest request("https://www.google.pl/");
if(headers.size() > 0) {
for (QMap<const char*, const char*>::iterator i = headers.begin(); i != headers.end(); ++i)
request.setRawHeader(i.key(), i.value());
}
QNetworkAccessManager *manager = new QNetworkAccessManager();
manager->setCookieJar(this->cookies);
QNetworkReply *reply = manager->get(request);
QEventLoop loop;
QObject::connect(reply, SIGNAL(finished()), &loop, SLOT(quit()));
loop.exec();
QList<QNetworkCookie> cookies = reply->manager()->cookieJar()->cookiesForUrl(QUrl(reply->url()));
foreach(QNetworkCookie cookie, cookies)
{
this->cookies->insertCookie(cookie);
}
return reply->readAll().data();
}
QEventLoop is executed to get response in the same void. Is this creating new threads?

Answer 1

There are a few things wrong here:
Your application should have a single QNetworkAccessManager that all code uses, don't create one for every call, create one in main and pass that to where it is needed.
You need to delete QNetworkReply using deleteLater as explained in the manual.
Creating another event loop in a function is generally not a good idea. Create a slot on the class httpManager connected to the QNetworkAccessManager::finished(QNetworkReply * reply) signal, read the reply and call deleteLater from here.