[Boost-users] Re: boost::fsm, parameters to DestinationState

From: Jan Eickmann (je_at_[hidden])
Date: 2005-03-10 15:21:01

Andreas Huber wrote:
> Hi Jan
> 
>> when doing a transition using transit<myDestinationState>, I would
>> like to pass some parameters to myDestination.
> 
> 
> What is the ctor of myDestination going to do with them? Where do these 
> arguments come from? What did you do with them in the react function?
> 
>> Problem is, those
>> parameter-values will  not be known at compile time, so I can't just
>> pass them in as template-parameters to myDestinationState.
>> Of course I could just set some global (or static member member)
>> variable and read that from myDestinationState's constructor but this
>> doesn't feel like a very clean design.
>>
>> Any suggestions?
> 
> 
> There are various ways: Have a variable in an outer state, have one in 
> the FSM, use a transition action or avoid the problem altogether. What 
> exactly the best one is really depends on the source of your problem.
> 
> Regards,
> Andreas Huber

Thanks for the help so far,

I'll try to give some more information. In the application we are 
developing, we have a screen that is kind of like an encyclopedia. This 
screen is usually shown after the user presses a "more information" 
button in a popup dialog, etc.
That encyclopedia-screen is the state I want to transit to. Now what I 
want to do is tell that screen what entry to show.
In order to be able to get back to the original state, I put the 
"normal" GUI of the application in a state that has a deep-history.

So the common outer state would basicly be the FSM but I would rather 
avoid having a variable there as this would require changing the FSM 
itself everytime I want to add a similar screen that gets told from the 
outside what to do exactly.

I currently don't really see how I can avoid the problem altogether...

Regards,

Jan Eickmann