Created
April 16, 2019 20:40
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State machine using enums in Rust
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#[derive(Debug)] | |
enum State { | |
New(Option<String>), | |
Running(String), | |
Failure(Box<State>), | |
} | |
enum Event { | |
Open(String), | |
Run, | |
} | |
impl State { | |
// State transition logically consumes the state and event types | |
fn event(self, event: Event) -> Self { | |
match (&self, event) { | |
(State::New(_), Event::Open(s)) => State::New(Some(s)), | |
(State::New(Some(s)), Event::Run) => State::Running(s.to_owned()), | |
_ => State::Failure(Box::new(self)) | |
} | |
} | |
} | |
fn main() { | |
let mut machine = State::New(None); | |
let events = vec![ | |
Event::Open("foo".to_owned()), // new(none) -> new(some("foo")) | |
Event::Open("bar".to_owned()), // new(some("foo")) -> new(some("bar")) | |
Event::Run, // new(some("bar")) -> running | |
Event::Run, // running -> failure | |
]; | |
for event in events { | |
machine = machine.event(event); | |
dbg!(&machine); | |
} | |
} |
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