This chapter describes how to work with machinae if you want to use trait objects for your states. This allows you to better organize the states using multiple types, but it's not as efficient since it uses dynamic dispatch and allocates on the heap.

You'll need to import the following machinae types, plus your argument, error and event types:

use machinae::{DynMachine, DynResult, DynState, Trans};
use some_module::{Argument, Error, Event};

Next, define the structs you want to use as states:

struct State1;

struct State2(i32);

Because we're not using a single type here, we can't use State directly, but rather implement DynState for every struct. A boxed DynState automatically implements State.

# #![allow(unused_variables)]
#fn main() {
impl DynState<Argument, Error, Event> for State1 {
    fn start(&mut self, args: Argument) -> DynResult<i32, Error, Event> {
        Ok(Trans::None)
    }

    fn update(&mut self, args: Argument) -> DynResult<i32, Error, Event> {
        Ok(Trans::Switch(Box::new(State2(42))))
    }
}

impl DynState<i32, Error, Event> for State2 {
    fn start(&mut self, args: Argument) -> DynResult<i32, Error, Event> {
        Ok(Trans::Quit)
    }
}
#}

And finally you can use the DynMachine typedef to create a new state machine:

let mut machine = DynMachine::new(Box::new(State1));