QtThread

GrahamL

Hi
I have been reading about QtThread and there seems to be a lot of discussion about how to correctly use this class. i.e. should developers derive from QtThread or provide an QObject and move this object to a thread.
The examples provided with Qt5 derive from QtThread whereas there is a lot of chatter on the web saying this is not the correct way.

Can anyone provide some definitive answers on how developers are to use QtThread?

Thanks

SGaist

Hi,

The latest documentation of "QThread":http://qt-project.org/doc/qt-5/qthread.html shows both methods and in which circumstances they can/should be used. Is this what you were looking for ?

GrahamL

Thanks - I'll read this

GrahamL

Hi
I need to implement a producer/consumer pattern
As you know Qt provides 2 examples (mutexes and semaphores) and both derive from QtThread.
I guess my question now becomes
'to implement a producer/consumer pattern must I derive from QtThread?'

Any thoughts?

Thanks

Jeroentjehome

Hi,
It all depends on the implementation use of your multi threaded design!
First read this:
"Thread basics":http://qt-project.org/doc/qt-4.8/thread-basics.html
It goes into QThread and QtConcurrent use and implementation. QThread is very low level and IYAM QtConcurrent is easier to implement.

GrahamL

Hi
Thats a great resource

Thanks

JKSH

Hi,

[quote author="Jeroentje@home" date="1389610503"]Hi,
It all depends on the implementation use of your multi threaded design![/quote]
Agreed!

A few years ago, subclassing QThread was declared "wrong" because lots of people did it wrong.

However, there are still valid cases where subclassing QThread is "better" than using moveToThread().

For a comparison of different ways to use threads, see http://qt-project.org/doc/qt-5/threads-technologies.html

[quote]First read this:
"Thread basics":http://qt-project.org/doc/qt-4.8/thread-basics.html
It goes into QThread and QtConcurrent use and implementation. QThread is very low level and IYAM QtConcurrent is easier to implement.
[/quote]Unfortunately, that link is outdated and incomplete. Importantly, do NOT follow Example 3 -- it is an example of the definitely-bad way of using QThread!

The updated, cleaned-up version is at http://qt-project.org/doc/qt-5/thread-basics.html . Follow the links inside it too -- they take you to other helpful pages on the topic of multithreading.

[quote author="GrahamL" date="1389606322"]I need to implement a producer/consumer pattern
As you know Qt provides 2 examples (mutexes and semaphores) and both derive from QtThread.
I guess my question now becomes
'to implement a producer/consumer pattern must I derive from QtThread?'[/quote]Did you meant wait conditions and semaphores? There are the 2 examples of the producer/consumer pattern that I know of:

These examples subclass QThread, and that's fine.

GrahamL

Ok
I am starting to understand
Thanks everyone