oxide-mvu

A lightweight Model-View-Update (MVU) runtime for Rust with no_std support.

Documentation
Crates.io

Note: This framework is under active development. APIs should not be considered stable.

What is MVU?

The Model-View-Update pattern (also known as the Elm Architecture) structures applications as a pure functional loop:

Model: Immutable state representing your entire application
Update: Pure function transforming (Event, Model) → (Model, Effect)
View: Pure function deriving renderable Props from the Model

This architecture eliminates implicit state mutation, making your application predictable, debuggable, and testable.

Why oxide-mvu?

Pure functional state management - All state transitions are explicit and testable
Unidirectional data flow - Easy to reason about and debug
Lock-free concurrency - Events from any thread without mutex overhead
Async runtime agnostic - Works with tokio, async-std, smol, or custom executors
Built-in testing utilities - Comprehensive test helpers included
no_std support - Suitable for embedded systems (requires alloc)

Quick Start

Installation

[dependencies]
oxide-mvu = "0.4.2"

For embedded systems (no_std):

[dependencies]
oxide-mvu = { version = "0.4.2", features = ["no_std"] }

use oxide_mvu::{Emitter, Effect, MvuLogic, MvuRuntime, Renderer};

// 1. Model the system, its behavior, and the renderable
//    projection (Props) including any controls.
#[derive(Clone)]
enum Event {
    Increment,
}

#[derive(Clone)]
struct Model {
    count: i32,
}

struct Props {
    count: i32,
    on_click: Box<dyn Fn()>,
}

// 2. Implement application logic
struct Logic;

impl MvuLogic<Event, Model, Props> for Logic {
    fn init(&self, model: Model) -> (Model, Effect<Event>) {
        (model, Effect::none())
    }

    fn update(&self, event: Event, model: &Model) -> (Model, Effect<Event>) {
        match event {
            Event::Increment => (Model { count: model.count + 1 }, Effect::none()),
        }
    }

    fn view(&self, model: &Model, emitter: &Emitter<Event>) -> Props {
        let emitter = emitter.clone();
        Props {
            count: model.count,
            on_click: Box::new(move || emitter.clone().try_emit(Event::Increment)),
        }
    }
}

// 3. Implement a renderer to display Props.
struct MyRenderer;

impl Renderer<Props> for MyRenderer {
    fn render(&mut self, props: Props) {
        println!("Count: {}", props.count);
    }
}

// 4. Run the application
async fn main() {
    let runtime = MvuRuntime::builder(
        Model { count: 0 },
        Logic {},
        MyRenderer {},
        |fut| { tokio::spawn(fut); },
    ).build();

    runtime.run().await;
}

Examples

Working examples demonstrating oxide-mvu in various environments:

cortex-m-single-core - Complete no_std embedded example running on nRF52840 (Cortex-M4F) with Embassy async runtime, emulated via Renode.

See the examples directory for more.

Testing

The MVU pattern makes applications easy to test. State transitions are pure functions:

#[test]
fn test_increment() {
    let logic = Logic;
    let model = Model { count: 0 };
    let (new_model, _effect) = logic.update(Event::Increment, &model);
    assert_eq!(new_model.count, 1);
}

For integration testing, use the testing feature:

[dev-dependencies]
oxide-mvu = { version = "0.4.2", features = ["testing"] }

This provides:

TestMvuRuntime - Runtime with manual event processing control
TestRenderer - Renderer that captures Props for assertions
create_test_spawner() - Test-friendly task spawner

use oxide_mvu::{TestMvuRuntime, TestRenderer, create_test_spawner};

#[test]
fn test_full_mvu_loop() {
    let renderer = TestRenderer::new();
    let runtime = TestMvuRuntime::builder(
        Model { count: 0 },
        Logic {},
        renderer.clone(),
        create_test_spawner(),
    ).build();

    let mut driver = runtime.run();

    // Verify initial render
    assert_eq!(renderer.count(), 1);
    renderer.with_renders(|renders| {
        assert_eq!(renders[0].count, 0);
    });

    // Trigger the Props callback and advance the runtime
    renderer.with_renders(|renders| (renders[0].on_click)());
    driver.process_events();

    // Verify update
    assert_eq!(renderer.count(), 2);
    renderer.with_renders(|renders| {
        assert_eq!(renders[1].count, 1);
    });
}

See the tests directory for more examples.

Learn More

API Documentation - Complete API reference with examples
Examples - Working examples in various environments
Tests - Tests demonstrating common patterns

License

Licensed under the Apache License, Version 2.0 (LICENSE or http://www.apache.org/licenses/LICENSE-2.0)

oxide-mvu 0.4.2