yuk1ty/statemachine-rs

Zero dependency state machine implementation for Rust

statemachine-rs

A zero dependency crate to implement state machine.

Usage

Let's have a look at the following simple example. This example shows the state machine can transit its number (it called current_state in this machine) from given string ("next") and then, it produces outputs.

use statemachine_rs::machine::{
    builder::{BasicStateMachineBuilder, StateMachineBuilder},
    StateMachine,
};

fn main() {
    let sm = BasicStateMachineBuilder::start()
        .initial_state(1)
        .transition(|state, input| match (state, input) {
            (1, "next") => 2,
            (2, "next") => 3,
            _ => unreachable!(),
        })
        .build()
        .unwrap();

    assert_eq!(1, sm.current_state());
    sm.consume("next");
    assert_eq!(2, sm.current_state());
}

You can assemble your state machine by using statemachine_rs::machine::builder::BasicStateMachineBuilder. BasicStateMachineBuilder::initial_state() initializes the initial state of its machine. BasicStateMachineBuilder::transition() defines the transition model.

Of cource we can use enums for representing states and inputs. Let's have a look at another example.

The following example describes if you press the button, the state turns to be On. Otherwise, Off.

use statemachine_rs::machine::{
    builder::{BasicStateMachineBuilder, StateMachineBuilder},
    StateMachine,
};

#[derive(Clone, Debug, PartialEq)]
enum ButtonState {
    On,
    Off,
}

enum Input {
    Press,
}

fn main() {
    let sm = BasicStateMachineBuilder::start()
        .initial_state(ButtonState::Off)
        .transition(|state, input| match (state, input) {
            (ButtonState::On, Input::Press) => ButtonState::Off,
            (ButtonState::Off, Input::Press) => ButtonState::On,
        })
        .build()
        .unwrap();

    assert_eq!(ButtonState::Off, sm.current_state());
    sm.consume(Input::Press);
    assert_eq!(ButtonState::On, sm.current_state());
}

License

MIT

Contribution

All contributions are welcome.

If you have an idea to improve this crate, create new issue or submit new pull request.

License: MIT

statemachine-rs's Issues

Examples don't compile: `StateMachineBuilder::start()` leads to cannot infer type

The examples in the README.md file don't work as is. Using rustc 1.60.0 I get:

error[E0282]: type annotations needed
 --> src/main.rs:4:14
  |
4 |     let sm = StateMachineBuilder::start()
  |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type
  |
  = note: type must be known at this point