[Qt-interest] Qt State machine framework

[Mandeep Sandhu]

On Fri, Mar 12, 2010 at 6:34 PM, Mandeep Sandhu
<mandeepsandhu.chd at gmail.com> wrote:
> I had one more requirement, which I can't see a clean way to implement...
>
> Say my FSM has 4 states: s1, s2, s3 and s4.
>
> s4 can be entered from either s1, s2 or s3.
>
> When in s4, on an event, I need to go back to the state from which I
> had entered s4.
>
> So the transition from s4 has to take into account from which state it
> was entered so that it can go back to it. I can store the state using
> the onExit() callback....but how do I make it go to the required
> state. I can't use the setTarget() api since this has to be determined
> while the FSM is running and not before when i'm setting up the
> transitions.
>
> Any thoughts?

I do! :)

I forgot to mention that s1, s2 and s3 are entered on my custom events
e1, e2 and e3 respectively.

So while writing this a soln came to mind:

When I have to exit s4, I can check some var that I have set (which
stores the state from which s4 was entered) and do a
postEvent(e1/e2/e3) to transition back to the original state.

Or is there a better way?

-mandeep

>
> Thanks,
> -mandeep
>
>
> On Fri, Mar 12, 2010 at 11:03 AM,  <noam.rosenthal at nokia.com> wrote:
>> Hi Mandeep
>> Actually both things are supported!
>>
>> 1. http://doc.trolltech.com/4.6/qabstracttransition.html#triggered: A signal that gets emitted when a transition is triggered. You can then query the tranistion's source/target properties.
>> 2. http://doc.trolltech.com/4.6/qstatemachine.html#configuration: QStateMachine::configuration(), returns a set of current states.
>>
>> Hope this answers your question,
>
>>
>> Regards
>> No'am
>>
>>>-----Original Message-----
>>>From: qt-interest-bounces at trolltech.com
>>>[mailto:qt-interest-bounces at trolltech.com] On Behalf Of ext
>>>Mandeep Sandhu
>>>Sent: Friday, March 12, 2010 2:20 PM
>>>To: qt-interest at trolltech.com
>>>Subject: [Qt-interest] Qt State machine framework
>>>
>>>Hi All,
>>>
>>>I'm planning to implement a FSM for one of my apps using the
>>>Qt State machine framework. I have some requirements which
>>>somehow are not there in this frame work by default (maybe I'm
>>>missing something).
>>>They are:
>>>
>>>* I need to emit a signal whenever the FSM transitions from 1
>>>state to another. The signal emits the old state and the new state
>>>* I need to provide an API to a caller to let it know what the
>>>current state the FSM is in.
>>>
>>>For the 1st requirement I could not find an existing API's
>>>which can do that (only started, stopped, finished signals are
>>>emitted by the qtstatemachine class).
>>>
>>>I can think of many ways to do it, eg: create my own
>>>transition and emit a signal in it's onTransition() method,
>>>create my own state (subclassing the QtAbstractState and emit
>>>a signal in it's onEntry method...though I won't have the
>>>previous state then...)
>>>
>>>For the second part I need to keep updating some member of my
>>>class to keep track of the current state (lame).
>>>
>>>Any suggestions on better approaches (if any)?
>>>
>>>Thanks,
>>>-mandeep
>>>_______________________________________________
>>>Qt-interest mailing list
>>>Qt-interest at trolltech.com
>>>http://lists.trolltech.com/mailman/listinfo/qt-interest
>>>
>