[Boost-users] Re: Weird behaviour when changing states in boost::fsm

From: Andreas Huber (ahd6974-spamgroupstrap_at_[hidden])
Date: 2005-03-02 04:53:57

Hi Jan

> I realized a weird behaviour when using boost::fsm.
> Here's my state setup:
> 
> I have a parent state which has two substates. One is basicly a noop as 
> InnerInitial, the other is and OptionsDialog.
> Now, in a custom_reaction's react function in the parent state, I call 
> transit<OptionsDialog> in order to go to the OptionsDialog-substate.
> What happens is that the parentstate itself is destroyed and reentered, 
> then it enters the OptionsDialog state.

As Darryl has already pointed out (Thanks Darryl!) this is expected and in 
line with the behavior defined by UML/Harel.

> Something similar happens when I use transit<ParentState> to go back to 
> the ParentState (which should automatically enter the InnerInitial, 
> no?).

Yes.

> It exits the OptionsDialog, then exits ParentState and reenters 
> ParentState (I haven't checked if it enters the InnerInitial).

Again, all expected and it should enter InnerInitial.

> If in the OptionsDialog, I do a transit<NoOpInnerInitial> it just goes 
> there without first destroying the parent-state (just exits 
> OptionsDialog but not ParentState).
> Is this the expected behaviour, if so, could someone explain how to get 
> the desired behaviour?

IIUC, it seems that you don't need the parent state, as you basically just 
have 2 states (ShowOptionsDialog/DontShowOptionsDialog), with 2 or 3 
transitions between these states. Then again, this obviously depends on 
whether it is just a toy example or a part of a bigger FSM. In the latter case 
you'd need to give a rough description of the desired behavior of the whole 
FSM...

Regards,

Andreas