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ffux

Flux implementation for Functional Reactive Programming with Bacon.js or RxJS.

Motivation

Flux is the hottest keyword in the React circles nowadays. Although the latest Flux implementations have moved towards functional paradigms they still introduce a lot of boilerplate, complexity and potential bugs that could be avoided by adopting Functional Reactive Programming.

The goal of this project is to remove all of the complexity and provide a simple way to harness the power of FRP by using the mental model of Flux.

Why to choose ffux?

Here are some points to choose ffux over other Flux implementations:

• Expressive - All the power of FRP is on your hand
• Extremely simple - Only two functions needed: createStore and ffux
• Library/view agnostic - Drop React and use with jQuery if you want ;-)
• Explicit - See the structure of your application with a single glance
• Lightweight - The whole library is under 200 LOC of ES6. :-)

Well... You must see it yourself:

const React = require("react"),
      ffux  = require("ffux")
      
const {Listener} = require("ffux/react")

const {createStore} = ffux

const Counter = createStore({
  actions: ["incrementN", "decrementOne"],
  state: (initialState, actionStreams) => {
    const {incrementN, decrementOne} = actionStreams
    // All Bacon.js tricks are permitted here!
    return incrementN
      .merge(decrementOne.map(-1))
      .scan(initialState, (state, delta) => state + delta)
  }
})

const CounterApp = React.createClass({
  render() {
    // ffux model contains two properties:
    //   * "state" contains the current state of the application
    //   * "actions" contains the action creators that can be invoked
    const {counter} = this.props.state

    // action creators are just functions that can be invoked with arguments normally
    const {counter: {incrementN, decrementOne}} = this.props.actions

    return (
      <div>
        <div>Counter: {counter}</div>
        <button onClick={() => incrementN(2)}>+2</button>
        <button onClick={() => decrementOne()}>-</button>
      </div>
    )
  }
})

const App = React.createClass({
  render() {
    return (
      <Listener initialState={{counter: 10}}
                dispatcher={state => ffux({counter: Counter(state.counter)})}>
        <CounterApp />
      </Listener>
    )
  }
})

React.render(<App />, document.getElementById("app"))

How to use?

Install dependencies with npm and start coding. For Bacon.js users:

npm i --save ffux baconjs

For RxJS users:

npm i --save ffux rx

API

ffux is designed to be used with ES6 but it can be used with ES5 as well. In order to to use fflux you must require it to your project:

If you are using Bacon.js:

const ffux = require("ffux")

If you are using RxJS:

const ffux = require("ffux/rx")

createStore({[actions,] state}) -> StoreDef

Creates a new store definition having the given actions and state stream.

Function takes object that can have two fields:

• state : Mandatory field that returns a Bacon.Property or Rx.Observable
• actions : Optional array that contains store's actions. These actions are passed to the state function as EventStreams / Observables

// Bacon.js
const Counter = ffux.createStore({
  actions: ["increment", "resetAsync"],
  // Parameters in state initialization function are:
  //  1. initial state
  //  2. action streams of this store (Bacon.EventStreams) mapped behind their names
  //  3. dependencies if any (see below)
  state: (counter, {increment, resetAsync}) => {
    // Here comes all the business logic of the store!
    // You are free to implement the data flow by using whatever FRP means you want
    const resetS   = resetAsync.delay(1000)
    const counterP = Bacon.update(counter,
      [increment], (state, delta) => state + delta,
      [resetS],    _ => 0
    )
    // the only restriction of the store is that it must return Bacon.property
    return counterP
  }
})

// RxJS
const Counter = ffux.createStore({
  actions: ["increment"],
  // same parameters as Bacon.js but now actions Rx.Observable instances
  state: (counter, {increment}) => {
    // state function must return an Rx.Observable
    return increment
      .scan(counter, (state, delta) => state + delta)
      .startWith(counter)
  }
})

ffux({<prop1>: Store, <prop2>: Store, ...}) -> Dispatcher

By using the StoreDef functions, you can instantiate actual store instances. In order to instantiate a store instance, you must call StoreStatefunction with the store's dinitial state:

const counter = Counter(10)
const Filter  = Filter("")  // another store

Once you've created the store instances you can use them to form your application state model. State model is just a flat JavaScript object containing store instances as values. This state model should reflect your (initial) state

const stateModel = {counter: Counter(10), filter: Filter("")}

You can create a ffux dispatcher by using the state model. The created dispacher has one method: .listen(callback). It can be used to listen your state changes. When the application state changes, a {state, actions} object containing the current state (schema reflects the state model) and action creators is passed to the callback function.

const dispatcher = ffux({counter})
dispatcher.listen(({state, actions}) => {
  // state == {counter: 10}
  // actions == {counter: {increment: <function>, resetAsync: <function>}}
  React.render(<MyApp state={state} actions={actions} />, ...)
})

Action creators

After you have created the dispatcher instance and started to listen the state model changes, you can use your stores' action creators. ffux creates these action creators automatically based on your StoreDef actions. These action creators are just plain functions that can be accessed from inside the dispacher.listen callback:

const Filter = ffux.createStore({
  actions: ["resetFilter"],
  state: (initialState, {resetFilter}) => {
    ...
  }
})

ffux({filter: Filter("")}).listen(({state, actions}) => {
  const resetFilter = actions.filter.resetFilter
  console.log(resetFilter) // => "function"
})

Action creators can be invoked with either zero, one or many parameters. When action creator is invoked with zero or one parameter then that parameter is passed to the action event stream as it is:

const Filter = ffux.createStore({
  actions: ["resetFilter"],
  state: (initialState, {resetFilter}) => {
    const trimmed = resetFilter.map(value => value.trim())
    ...
  }
})

// and usage inside your app
resetFilter("tsers")

Because event streams emit single events, multiple parameters are converted into an array that is passed to the event stream:

const Filter = ffux.createStore({
  actions: ["resetFilter"],
  state: (initialState, {resetFilter}) => {
    const trimmedAsync = resetFilter.flatMap(([value, timeout]) => ...)
    ...
  })
})
// and usage inside your app
resetFilter("tsers", 1000)

Flattening actions creators

By default, action creators are passed using the same schema as the state model. However, you can flatten them into actions object by passing flatActions = true option to the dispatcher. In that case remember that if action creator names clash, an error is thrown during dispatcher initialization:

const dispatcher = ffux({counter, filter}, {flatActions: true})
dispatcher.listen(({state, actions}) => {
  // actions == {increment: <function>, resetAsync: <function>, resetFilter: <function>}
  React.render(<MyApp state={state} actions={actions} />, ...)
})

Declaring dependencies between stores

In complex applications, dependencies are inevitable. Normal Flux implementations use signals and publish-subscribe to resolve this. This method provides extremely decoupled components but it has a major drawback: when dependencies become more complex, their management becomes chaotic and unpredictable because causations are not visible, thus there are high possibility to introduce e.g. cyclic dependencies.

ffux takes another approach: dependencies between stores are declared explicitly. This ensures you to think about responsibilities of your stores and reduce the possibility of circular dependencies and such kind of bugs.

In ffux you can declare dependencies during the store instantiation by passing the dependencies as a second parameter to the store. They can be anything - other stores, function or constants.

const todos = Todos([], {...here comes the dependencies...})

Stores are event streams!

This is essential when defining dependencies. Since the stores are event streams, you can treat them like actions. Imagine that you have to-do items that depend on the current filter value (in order to detect which items to display). Since the Filter store is an event stream, you can pass it as a dependency to the Todos store and get filter changes directly:

const Todos = createStore({
  state: (items, {}, {filter}) => {
    // every time when filter changes, it will run the filtering again, thus
    // causing a state change with the new displayed items
    return Bacon.combineTemplate({items, filter})
      .map(({items, filter}) => items.filter(it => it.indexOf(filter) !== -1))
  }
})

// pass filter like any other dependency
const filter = Filter("")
const todos  = Todos([], {filter})
ffux({todos, filter}).listen(...)

Using React helper component

ffux provides a helper component for React development: <Listener>. Listener takes two properties: initialState and dispatcher. The first one is a JavaScript object that represents the initial state of your application. The second one is a function (state) => Dispatcher building a dispatcher instance from state object.

Surround your application component with Listener: state and actions are propagated automatically to your application component.

const {Listener} = require("ffux/react")

const App = React.createClass({
  render() {
    return (
      <Listener initialState={{counter: 10}}
                dispatcher={state => ffux({counter: Counter(state.counter)})}>
        <MyAppComponent />
      </Listener>
    )
  }
})

React.render(<App />, document.getElementById("app"))

Hot (re)loading

Yes. Listener component is hot-reloadable by default.

Isomorphic app development

ffux has a native support for isomorphic application development. When you have created your ffux dispatcher, you can get the initial state with .take(callback) method and use the fetched model to render your application in your server:

// appState.js
export default function appState({filter: initFilter = "", todos: initTodos = []}) {
  const filter = Filter(initFilter)
  const todos  = Todos(initTodos, {filter})
  return ffux({todos, filter})
}

In the server:

// server.js
const state = loadFromDB()
appState(state).take(model => {
  res.send(`<html>
              <head></head>
              <body>
                <div id="app">${React.renderToString(<YourApp {...model} />)}</div>
                <script type="text/javascript">
                  window.INITIAL_STATE = ${JSON.stringify(model.state)};
                </script>
                <script type="text/javascript" src="site.js"></script>
              </body>
            </html>`)
})

And in the browser:

// site.js
appState(window.INITIAL_STATE).listen(model => {
  React.render(<YourApp {...model} />, document.getElementById("app"))
})

For more information, see isomorphic examples from examples folder.

Stopping the Dispatcher

Dispatcher .listen method returns stop function that can be invoked in order to stop the event listening. After stop method is called, no new events are dispatched.

const dispatcher = ffux(...)
const stop = dispatcher.listen(model => { ... })

// you can stop listening events by calling the returned stop function
stop()

Normally you shouldn't need to call the stop method from your application but if you are implementing e.g. your own hot reloading functionality, it may be useful.

License

MIT