Adding transition guards? about smacc2 HOT 2 CLOSED

Hello.
We already talked about that idea two years ago. And that is not hard to implement.
Personally, I like the proposal and follows the UML state machine standard.

The main argument why we did not implemented that is because it overlaps the functionality and responsibility of the StateReactors that potentially can receive events and generate other events. The suggested way to do that at the moment is to make a state reactor or use the conditional state reactor.

The good point of state reactors is that they are reusable pieces of code (against inline transition guards).

Nonetheless I think we could find a way to integrate this feature.

from smacc2.

Very fair. I'm currently working with the SrConditional approach. The main downsides are:

• The SMACC RTA display does not work. From memory, it shows something like internal_event with no lines from the state reactor inputs. Better RTA support for State Reactors or Guards would help.

• Verbosity. Here is a rather minimal example... I'm not sure if there is a better way to write this. I've had to write others where the state reactors depend on events from other state reactors - at this point, the code gets pretty tricky to follow.

// TRANSITION TABLE
typedef mpl::list<
    Transition<EvSomeInputEventWithGuard, StGuardedState, GUARDED_STATE>
> reactions;
   
...

void runtimeConfigure()
  {
    auto guard = [ = ](auto * ev) {
        (void)ev;
        
        // as an example, a behavior which contains some state used as a guard
        auto cbSomeBehaviorWithState =
          this->getOrthogonal<OrSomeOrthogonal>()->getClientBehavior<CbSomeBehavior>();
          
        // this is used to publish notifications of transitions onto a ros topic
        auto cbPublisher =
          this->getOrthogonal<OrSomePublisher>()->getClientBehavior<CbSomePublisher>();
          
        // guard checks
        if (!cbSomeBehaviorWithState->value) {
          cbPublisher->publish("Cannot transition because the state stored in CbSomeBehavior says so");
          return false;
        }
      
        return true;
      };

    this->createStateReactor<
      SrConditional<EvSomeInputEvent>,
      EvSomeInputEventWithGuard,
      mpl::list<EvSomeInputEvent>
    >(guard);
 }

• doing things like cbPublisher->publish (using the SmaccPublisherClient) does not work reliably - I'm not sure why.

from smacc2.