<![CDATA[Destroying/disconnecting a QTimer initialized in another function]]>Hi. I have a QTimer on the heap that is created every time a certain function is called. I would like to make sure I only have one of these QTimers by destroying the previous QTimer every time at the start of that certain function being called. This is how the Timer is made:

void ApplicationSettings::on_combo_changeBar_activated(int index){
    QTimer *timer = new QTimer(this);

    int seconds;
    switch (index){     //Written for redundancy. Future values are probably not gonna be in 2s.
    case 0:
        seconds = 1;
        break;
    case 1:
        seconds = 2;
        break;
    case 2:
        seconds = 4;
        break;
    case 3:
        seconds = 6;
        break;
    case 4:
        seconds = 8;
        break;
    default:
        seconds = 2;
    }
    qDebug() << seconds;
    ui->progressBar->setValue(0);

    connect(timer, &QTimer::timeout, this, [=](){this->otherFunction();});
    timer->start(seconds*10);
}

How can I destroy this QTimer the next time this function is called, such that there will only be one at all times? I wasn't able to find any documentation in the QTimer documentation.

]]>https://forum.qt.io/topic/140338/destroying-disconnecting-a-qtimer-initialized-in-another-functionRSS for NodeTue, 12 May 2026 21:13:20 GMTWed, 26 Oct 2022 13:45:25 GMT60<![CDATA[Reply to Destroying/disconnecting a QTimer initialized in another function on Wed, 26 Oct 2022 18:23:15 GMT]]>Hi,

In addition to my fellows, are you looking to just restart that timer ?
If so, then @mchinand solution is the most simple and effective beside having your QTimer as object member rather than pointer.

]]>https://forum.qt.io/post/734175https://forum.qt.io/post/734175Wed, 26 Oct 2022 18:23:15 GMT<![CDATA[Reply to Destroying/disconnecting a QTimer initialized in another function on Wed, 26 Oct 2022 17:11:05 GMT]]>@Dummie1138 said in Destroying/disconnecting a QTimer initialized in another function:

whether there is a way to simply destroy the timer when the function is redeclared.

As @Christian-Ehrlicher says, we do not know what "redeclared" means here.

Assuming you mean when this function is called again. To destroy (or reset) the timer in the function you will need a variable which refers to the timer. You cannot have a function local variable retain its value between calls (don't use static here). So you will need to store that reference variable outside the function somewhere. That is why it would need to be a class variable.

]]>https://forum.qt.io/post/734171https://forum.qt.io/post/734171Wed, 26 Oct 2022 17:11:05 GMT<![CDATA[Reply to Destroying/disconnecting a QTimer initialized in another function on Wed, 26 Oct 2022 14:45:12 GMT]]>@Dummie1138 said in Destroying/disconnecting a QTimer initialized in another function:

when the function is redeclared.

What does this mean?

]]>https://forum.qt.io/post/734158https://forum.qt.io/post/734158Wed, 26 Oct 2022 14:45:12 GMT<![CDATA[Reply to Destroying/disconnecting a QTimer initialized in another function on Wed, 26 Oct 2022 14:05:52 GMT]]>@mchinand Thank you very much for the response. I am aware that I can declare my timer as part of my class, but I was wondering whether there is a way to simply destroy the timer when the function is redeclared.

This function is meant to be declared every 20-80 mills, btw.

]]>https://forum.qt.io/post/734157https://forum.qt.io/post/734157Wed, 26 Oct 2022 14:05:52 GMT<![CDATA[Reply to Destroying/disconnecting a QTimer initialized in another function on Wed, 26 Oct 2022 14:05:21 GMT]]>Also, note that the start method parameter is in milliseconds and there are 1000 milliseconds in a second.

]]>https://forum.qt.io/post/734156https://forum.qt.io/post/734156Wed, 26 Oct 2022 14:05:21 GMT<![CDATA[Reply to Destroying/disconnecting a QTimer initialized in another function on Wed, 26 Oct 2022 14:00:38 GMT]]>Have your timer object be a private member of your class and then do:

void ApplicationSettings::on_combo_changeBar_activated(int index){
   if (timer == nullptr){// or instantiate it in the constructor
      timer = new QTimer();
      connect(timer, &QTimer::timeout, this, [=](){this->otherFunction();});
   }
   if (timer->isActive()){
      timer->stop();
   }
   .
   .
   .
   timer->start(seconds*10);
}
]]>https://forum.qt.io/post/734154https://forum.qt.io/post/734154Wed, 26 Oct 2022 14:00:38 GMT