Crate mode[][src]

Expand description

A simple and effective state machine library, written in in idiomatic, 100% safe, stable Rust code.

This library provides three main types, Automaton, Mode, and Family, which facilitate the creation of finite state machines. An Automaton can be used to quickly create a state machine over some Family of concrete types that implement the Mode trait. This can contain either:

  • a single, concrete type representing all states in the state machine, e.g. a struct or an enum, or
  • one or more separate types that all implement some common dyn Trait, with each type representing a distinct state in the state machine.

The Automaton keeps track of a current instance of Mode, and provides external access to any members that are common to all Modes in the Family. A flexible transition system provides a way to swap in a new Mode in the same Family, when ready, and is designed such that state from the current Mode can be moved directly into the new Mode being created. This can help prevent spikes in memory usage when transitioning between Modes that own large amounts of data.


  • For a simple example of how to use this library to implement a simple state machine over a single, concrete type, please see examples/
  • For a more advanced example demonstrating a state machine over several types in the same Family, please see examples/
  • For an example demonstrating how to pass context into and out of transition functions, please see examples/

You can run the examples using the following Cargo commands:

cargo run --example enum
cargo run --example activity
cargo run --example turing

Getting started

A good place to start reading would be the Automaton documentation, followed by Mode and then Family.


Represents a state machine over a set of Modes within the same Family.


A meta-trait defining the common Base type and Mode storage conventions used by a related group of Mode implementations. Modes can only transition to other Modes within the same Family, i.e. where both Modes share the same Family associated type.

Trait that defines a state within some Family, and can be made active in an Automaton.