Elm Architecture Examples in Rust

This is a collection of examples from https://guide.elm-lang.org implementing "The Elm Architecture", sometimes also called the Elm pattern. The examples are implemented as simple console applications instead of being web apps. So, instead of clicking on some buttons, you usually press keyboard keys, and instead of showing HTML, there is just some output to console.

One difference to the pattern is the signature of the function subscriptions. In Elm it takes a model and depending on it, it returns subscriptions. The function is executed every time the model is updated. This makes it possible to remove or cancel subscriptions previously created.

In Rust, the signature is:

fn subscriptions(Model) -> (Model, Sub<Msg>);

The function is called only once on initialization. The initial model is passed and returned again, since on contrary to Elm we are not having a global state but store everything in the model (e.g. Elm tracks open websockets in its runtime and so allows magically to send values, even without having a channel to the socket.)

Practically, it should be possible to call the function after each update of the model and update current subscriptions, however, this also means that we need some kind of tracking and identification of subscriptions already created. Instead, we track a subscription with tokio's cancellation tokens (any other kind of a cancellation token of a stream is also possible); see the time example.

How to run

cargo run --bin time
cargo run --bin random
cargo run --bin http
cargo run --bin websocket

License

• Apache License, Version 2.0, (LICENSE-APACHE or
  http://www.apache.org/licenses/LICENSE-2.0)
• MIT License (LICENSE-MIT or
  http://opensource.org/licenses/MIT)

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this document by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.