How can I access the payload from the control?

[positrigo-deps]

Hello,

first of all, thank you very much for your time working on this awesome library. We have enjoyed using it so far.

I'm trying to understand how to access a payload from the control, but I cannot figure it out. How can it be done?

Thanks, and have a nice day,

Alon

[andrew-gresyk]

Hi,
Thank you, glad you like it!

Currently, the way to access payloads is via transition history introspection:

The API is optional, needs #define HFSM2_ENABLE_TRANSITION_HISTORY.

• for guards: const auto& pendingTransitions = control.pendingTransitions();
• for other methods: const auto& currentTransitions = control.currentTransitions();

This gives a custom (range for friendly) array of transitions.
The payload for each transition can be accessed via const Payload* Transition::payload() const method.

There's a usage example in test_internal_payloads.cpp

[positrigo-deps]

thanks so much! I will look into it. Just a quick question already: will enabling this store all transitions indefinitely?

[andrew-gresyk]

Not indefinitely, only for the last update() or react()

Usually, the array will only have one transition.

However, it is possible to queue up multiple transitions for different prongs of an orthogonal region:

using FSM = M::OrthogonalRoot<R,
				M::Composite<C1,
					C1_A,
					C1_B,
					C1_C
				>,
				M::Composite<C2,
					C2_A,
					C2_B,
					C2_C
				>
			>;

fsm.changeTo<C1_B>();
fsm.changeTo<C2_B>();
fsm.update(); // or fsm.react<TEvent>();

Here, two transitions will be processed in parallel.

[andrew-gresyk]

Now, I have to say, I would rather prefer something simpler, e.g.:
control.payload()

The challenge comes from the fact that in a hierarchy, one transition request may activate multiple states, so matching a request to state type isn't trivial.
Hopefully something that can be improved in the future.

[positrigo-deps]

ah, interesting. I was trying to use AI to figure it out, and it always suggested this control.payload() API which it was hallucinating...