Question

I have a state machine for my npcs that is structured like the following,

execute state
[[[pred1 pred2....] state1]
 [[pred3 pred4....] state2]
 [[pred5 pred6....] staten]]

What happens is after current state completes, it starts iterating through the states/predicates list and as soon as a list of predicates that returns all true it will jump to the state that it is associated with.

Certain events can happen during all states, say player commands npc to go somewhere. Just like any other state transition I can check for a predicate and change state but adding the same piece of code to every state seems a bit lame. So I was wondering how people deal with events in state machines?

Answer 1

Just make a data structure like:

state1 -> event1, event2
state2 -> event1
state3 -> event2, event3

By the way, what you have outlined doesn’t look like a state machine. In state machine, next state depends on the previous one, so it would look like:

[state1, condition1] -> state2
[state1, condition2] -> state3
...

(condition is your set of predicates). You must also somehow assure that the transition is unique, i.e. that condition1 and condition2 cannot be fulfilled at the same time. Or take the first one which is true.