Crate reactive_state

This library is inspired by redux, and designed to be used within Rust GUI applications to manage centralised global state which behaves in a predictable way.

Example

The following is a simple example of how to use this system to manage state, and subscribe to changes to state.

use reactive_state::{ReducerFn, ReducerResult, Store, Callback};
use std::{cell::RefCell, rc::Rc};

/// Something to hold the application state.
#[derive(Clone)]
struct MyState {
    pub variable: u32
}

/// Some actions to perform which alter the state.
enum MyAction {
    Increment,
    Decrement
}

/// Some events that are fired during certain action/state combinations.
#[derive(Clone, Eq, PartialEq, Hash)]
enum MyEvent {
    IsOne,
}

/// A reducer to perform the actions, alter the state, and fire off events.
let reducer: ReducerFn<MyState, MyAction, MyEvent, ()> = |state, action| {
    let mut events: Vec<MyEvent> = Vec::new();

    let new_state = match action {
        MyAction::Increment => {
            let mut new_state = MyState::clone(state);
            new_state.variable = state.variable + 1;
            Rc::new(new_state)
        }
        MyAction::Decrement => {
            let mut new_state = MyState::clone(state);
            new_state.variable = state.variable - 1;
            Rc::new(new_state)
        }
    };

    if new_state.variable == 1 {
        events.push(MyEvent::IsOne);
    }

    ReducerResult {
        state: new_state,
        events,
        effects: vec![],
    }
};

// Set the initial state.
let initial_state = MyState {
    variable: 0u32
};

// Create the store.
let store = Store::new(reducer, initial_state);

// A test variable that will be altered by the callback.
let callback_invokes: Rc<RefCell<u32>> = Rc::new(RefCell::new(0u32));
let callback_invokes_local = callback_invokes.clone();

let callback = Callback::new(move |_state: Rc<MyState>, _event: Option<MyEvent>| {
    *(callback_invokes_local.borrow_mut()) += 1;
});

// Subscribe to state changes which produce the IsOne event.
store.subscribe_event(&callback, MyEvent::IsOne);

assert_eq!(0, store.state().variable);
assert_eq!(0, *RefCell::borrow(&callback_invokes));

// Dispatch an increment action onto the store, which will
// alter the state.
store.dispatch(MyAction::Increment);

// The state has been altered.
assert_eq!(1, store.state().variable);

// The callback was invoked.
assert_eq!(1, *RefCell::borrow(&callback_invokes));

store.dispatch(MyAction::Increment);

// The state has been altered.
assert_eq!(2, store.state().variable);

// The callback was not invoked, because the event IsOne
// was not fired by the reducer.
assert_eq!(1, *RefCell::borrow(&callback_invokes));

// Drop the callback, and it will also be removed from the store.
drop(callback);

store.dispatch(MyAction::Decrement);

// The state has been altered again.
assert_eq!(1, store.state().variable);

// The callback was dropped before the action was dispatched,
// and so it was not invoked.
assert_eq!(1, *RefCell::borrow(&callback_invokes));

Side Effects

Something that wasn’t covered in the example above, was the concept of side effects produced in the reducer. This is the fourth type parameter Effect on Store, and effects which are produced in the reducer are given to the store via the ReducerResult that it returns. Side effects are designed to be executed/handled by store middleware.

Optional Features

The following optional crate features can be enabled:

• "simple_logger" - Logging middleware in the simple_logger module which uses the log macros.
• "web_logger" - Logging middleware in the web_logger module, for applications running in the browser using wasm-bindgen.
• "yew" - Support for compatibility trait implementations on yew types.

Modules

middleware	Middleware used to modify the behaviour of a Store during a Store::dispatch(). This module also contains some simple middleware implementations which can be used as utilities in an application.
provider	yew

Structs

Callback	A wrapper for a callback which is notified of changes to Store State, and Events produced by the store.
CompositeReducer	A Reducer composed of multiple reducers.
Listener	A weak reference to a callback function (usually Callback) which is notified of changes to Store State, and Events produced by the store.
ReducerResult	The result of a Reducer::reduce() function.
Store	This struct is designed to operate as a central source of truth and global “immutable” state within your application.
StoreRef	A wrapper for an Rc reference to a Store.

Traits

AsListener	A trait to take a Callback or other custom callback type and produce a Listener, a weak reference to that callback.
Reducer	Using the reduce() method, implementors of this trait take an Action submitted to a store via Store::dispatch() and modifies the State in the store, producing a new State, and also producing events and effects associated with the Action and state modifications that occurred.

Type Definitions

ReducerFn

A wrapper for a function that implements the Reducer trait.