[Qt-interest] QThread vs QTimer for polling

[Martin Hofius]

Am Samstag, 27. Februar 2010 schrieb Mandeep Sandhu:
> Hi All,
>
> I'm using Qt on an embedded platform.
>
> My application is required to poll a particular h/w component for
> status changes/monitoring. Basically my application wants to get the
> status of a certain commands given to the h/w (these commands don't
> have immediate effect and hence the need for polling). Polling must be
> done till the time the requested status is achieved OR the maximum
> number of retires have been exceeded. Once the app gets the status, no
> more polling is needed till it issues another command.
>
Hi,

> I can think of 2 ways of achieving this:
first question: does the 3rd party lib provide only non blocking access? 
If not then...

use QThread, send your command and make a blocking access in your thread. So 
the thread will do nothing (and cost nothing except memory) until the result 
comes from your h/w  - the you can send a signal to your main app or just 
send the next command in your thread.  I think this is the best case.

If this lib only provides non blocking access, using a thread will always cost 
more cpu cycles by the advance of sligtly more accuracy compared to a main 
event loop timer.

Martin