<![CDATA[Infinite condition checking]]>I have a task where a function is called and the first thing done in that is to call a bool function to check a condition before proceeding. If that condition is true the code proceeds and if not it returns.

But I need a way to periodically check that condition, if it ever returns that function will be called again.

bool condition()
{
...
    //return true or false;
}

void foo()
{
    if( ! condition)
        return;

...

}

I need to find a way to go back to foo in case condition ever returns true.

I thought about QEventLoop but I want more options.

Any help is appreciated. Thanks in advance!

]]>https://forum.qt.io/topic/123984/infinite-condition-checkingRSS for NodeFri, 06 Nov 2026 12:13:14 GMTFri, 19 Feb 2021 15:03:31 GMT60<![CDATA[Reply to Infinite condition checking on Tue, 23 Feb 2021 21:30:02 GMT]]>Order of destruction, code run during destruction, etc

Think of a database, you likely appreciate the fact that all operations are finalised before it stops so you don't have corrupted data when you restart it.

]]>https://forum.qt.io/post/646029https://forum.qt.io/post/646029Tue, 23 Feb 2021 21:30:02 GMT<![CDATA[Reply to Infinite condition checking on Mon, 22 Feb 2021 22:50:19 GMT]]>@SGaist @jsulm

Ending an application does not mean everything is destroyed instantly.

I have followed your suggestion, and now I am wondering, is this something that I have to always watch out for, is there a name for this kind of situation, a reference I can search?

And also, why is everything not destroyed instantly? What are the steps being taken? What is happening under the hood there? Any reference?

]]>https://forum.qt.io/post/645802https://forum.qt.io/post/645802Mon, 22 Feb 2021 22:50:19 GMT<![CDATA[Reply to Infinite condition checking on Mon, 22 Feb 2021 12:47:03 GMT]]>@jsulm ok thanks

]]>https://forum.qt.io/post/645731https://forum.qt.io/post/645731Mon, 22 Feb 2021 12:47:03 GMT<![CDATA[Reply to Infinite condition checking on Mon, 22 Feb 2021 06:15:19 GMT]]>@hbatalha said in Infinite condition checking:

is part of another class

Then put it there as member variable and stop it in destructor (or whenever needed).

]]>https://forum.qt.io/post/645669https://forum.qt.io/post/645669Mon, 22 Feb 2021 06:15:19 GMT<![CDATA[Reply to Infinite condition checking on Mon, 22 Feb 2021 06:11:19 GMT]]>@SGaist foo is not from the mainwindow, is part of another class, should I call stop in the destructor?

]]>https://forum.qt.io/post/645667https://forum.qt.io/post/645667Mon, 22 Feb 2021 06:11:19 GMT<![CDATA[Reply to Infinite condition checking on Sat, 20 Feb 2021 20:19:59 GMT]]>I don't know how long foo will take so you might not want for it to triggered when you end your application. Ending an application does not mean everything is destroyed instantly.

]]>https://forum.qt.io/post/645582https://forum.qt.io/post/645582Sat, 20 Feb 2021 20:19:59 GMT<![CDATA[Reply to Infinite condition checking on Sat, 20 Feb 2021 20:15:37 GMT]]>@SGaist didn't quite understand what you meant, when my application won't everything be stopped?

Also, I need to call foo only once when the timeout is emitted, took that example from the documentation.

]]>https://forum.qt.io/post/645581https://forum.qt.io/post/645581Sat, 20 Feb 2021 20:15:37 GMT<![CDATA[Reply to Infinite condition checking on Sat, 20 Feb 2021 20:00:14 GMT]]>You might want to consider making a QTimer member variable to be able to stop it for example when your application ends.

]]>https://forum.qt.io/post/645573https://forum.qt.io/post/645573Sat, 20 Feb 2021 20:00:14 GMT<![CDATA[Reply to Infinite condition checking on Sat, 20 Feb 2021 02:58:11 GMT]]>@SGaist That did solve my problem, thanks

void SomeClass::foo()
{
    if( ! condition)
    {
        QTimer::singleShot(5000, this, &SomeClass::foo);

        return;
    }
...

}
]]>https://forum.qt.io/post/645532https://forum.qt.io/post/645532Sat, 20 Feb 2021 02:58:11 GMT<![CDATA[Reply to Infinite condition checking on Fri, 19 Feb 2021 21:00:08 GMT]]>Sounds like a simple QTimer that calls foo regularly should do the job.

]]>https://forum.qt.io/post/645516https://forum.qt.io/post/645516Fri, 19 Feb 2021 21:00:08 GMT<![CDATA[Reply to Infinite condition checking on Fri, 19 Feb 2021 20:39:14 GMT]]>@SGaist something that calls condition regularly and if condition returns true then foo will be called

]]>https://forum.qt.io/post/645511https://forum.qt.io/post/645511Fri, 19 Feb 2021 20:39:14 GMT<![CDATA[Reply to Infinite condition checking on Fri, 19 Feb 2021 19:16:57 GMT]]>Hi,

Since foo checks the condition on each call, in fact, you want something that calls regularly foo ?

]]>https://forum.qt.io/post/645487https://forum.qt.io/post/645487Fri, 19 Feb 2021 19:16:57 GMT<![CDATA[Reply to Infinite condition checking on Fri, 19 Feb 2021 17:55:55 GMT]]>@raven-worx I am not using QML

but the extra logic is needed

Is there another way to do this?

]]>https://forum.qt.io/post/645480https://forum.qt.io/post/645480Fri, 19 Feb 2021 17:55:55 GMT<![CDATA[Reply to Infinite condition checking on Fri, 19 Feb 2021 15:32:47 GMT]]>@hbatalha
but the extra logic is needed, since you want to block the execution but actually you do not want to.
You can use WorkerScripts in QML which act like threads.

]]>https://forum.qt.io/post/645459https://forum.qt.io/post/645459Fri, 19 Feb 2021 15:32:47 GMT<![CDATA[Reply to Infinite condition checking on Fri, 19 Feb 2021 15:28:27 GMT]]>@raven-worx I thought about creating a loop that would run indefinitely until the condition returns true, if it ever does, meanwhile the user can use the application "normally".
But I don't want to use QEventLoop , because it adds an extra complexity to the program. That's why I want more options.

]]>https://forum.qt.io/post/645457https://forum.qt.io/post/645457Fri, 19 Feb 2021 15:28:27 GMT<![CDATA[Reply to Infinite condition checking on Fri, 19 Feb 2021 15:23:06 GMT]]>@hbatalha said in Infinite condition checking:

I thought about QEventLoop but I want more options.

elaborate

]]>https://forum.qt.io/post/645454https://forum.qt.io/post/645454Fri, 19 Feb 2021 15:23:06 GMT