declarative-state-machine

This project is WIP and currently in an unstable state

Ever wanted to write state machines in a declarative way with rusts mighty type safety? Well, here it is!

use declarative_state_machine::state_machine;

state_machine! {
    machine game_lifecycle {
        event run(_old: &mut State, _new: &mut State) {
            println!("Run application");
        }

        event pause(_old: &mut State, _new: &mut State) {
            println!("Pause application");
        }

        states {
            Stopped,
            Paused{ reason: String },
            Running(String),
        }

        event stop(_old: &mut State, _new: &mut State) {
            println!("Stop application");
        }

        transitions {
            Stopped => Running : run;
            Paused  => Running : run;
            Running => Paused  : pause;
            Running => Stopped : stop;
            Paused  => Stopped : stop;
        }
    }
}

fn main() {
    let _state_machine = game_lifecycle::Machine::new();
}

And all this with (quite) meaningful compiler messages:

warning: state has no transitions and will never be reached or cause deadlock on construction
  --> src/main.rs:17:13
   |
17 |             Unused,
   |             ^^^^^^
   |
   = help: add a transition to resolve: `Unused => OtherState : some_event`

For now all contents of state variants must implement the Default trait. Maybe this will change in the future.

The initial state of the state machine during construction is the first state in the states block.

TODOs

• Parse syntax of state machine
• Parse semantic of state machine
• Pass custom data to event handlers (otherwise handlers are quite useless...)
• Support doc-comments on event handlers and state variants
• Add serde support
• Add raft support
• Add no-std support
• Write tests
• Add travis CI configuration
• Cleanup syntax parsing code by using the syn crate
• Support superstates (nested state machines)

Want to help? Choose one of the above TODOs and create a pull request with your solution ;-)