extremely-simple-flux-demo

by ruanyf

Learn Flux from an extremely simple demo

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This demo helps you learn Flux architecture. It is inspired by Andrew Ray's great article Flux For Stupid People.

What is Flux?

Flux, invented by Facebook, is an architecture pattern for building client-side web applications.

It is similar to MVC architecture, but Flux's concept is much clearer than MVC's, and easier to learn.

How to Play?

Install the demo.

$ git clone [email protected]:ruanyf/extremely-simple-flux-demo.git
$ cd extremely-simple-flux-demo && npm install
$ npm start

Visit http://127.0.0.1:8080 with your browser.

You should see a button. Click it. That's all.

Core Concepts

According to Flux, an application should be divided into four parts.

  • Views: the UI layer
  • Actions: messages sent from Views (e.g. mouseClick)
  • Dispatcher: a place receiving actions, and calling callbacks
  • Stores: a place managing the Application's state, and reminding Views to update

The key feature of the Flux architecture is "one way" (unidirectional) data flow.

  1. User interacts with Views
  2. Views propagate an Action triggered by user
  3. Dispatcher receives the Action and updates the Store
  4. Store emits a "change" event
  5. Views respond to the "change" event and update itself

Don't get it? Take it easy. I will give you the details soon.

Demo Details

Now let us follow the demo to learn Flux.

First of all, Flux is usually used with React. So your familiarity with React is assumed. If not, I prepared a React tutorial for you.

Views

Our demo application's

index.jsx
has only one component.

// index.jsx
var React = require('react');
var ReactDOM = require('react-dom');
var MyButtonController = require('./components/MyButtonController');

ReactDOM.render( , document.querySelector('#example') );

In the above code, you might notice our component's name isn't

MyButton
, but
MyButtonController
. Why?

Because I use React's controller view pattern here. A controller view component holds all states, then passes this data to its descendants.

MyButtonController
's source code is simple.
// components/MyButtonController.jsx
var React = require('react');
var ButtonActions = require('../actions/ButtonActions');
var MyButton = require('./MyButton');

var MyButtonController = React.createClass({ createNewItem: function (event) { ButtonActions.addNewItem('new item'); },

render: function() { return ; } });

module.exports = MyButtonController;

In the above code,

MyButtonController
puts its data into UI component
MyButton
's properties.
MyButton
's source code is even simpler.
// components/MyButton.jsx
var React = require('react');

var MyButton = function(props) { return

New Item
; };

module.exports = MyButton;

In the above code, you may find

MyButton
is a pure component (meaning stateless), which is really the biggest advantage of the controll view pattern.

Here, the logic of our application is when user clicks

MyButton
, the
this.createNewItem
method will be called. It sends an action to Dispatcher.
// components/MyButtonController.jsx

// ... createNewItem: function (event) { ButtonActions.addNewItem('new item'); }

In the above code, calling the

createNewItem
method will trigger an
addNewItem
action.

What is an Action?

An action is an object which has some properties to carry data and an

actionType
property to identify the action type.

In our demo, the

ButtonActions
object is the place we hold all actions.

// actions/ButtonActions.js
var AppDispatcher = require('../dispatcher/AppDispatcher');

var ButtonActions = { addNewItem: function (text) { AppDispatcher.dispatch({ actionType: 'ADD_NEW_ITEM', text: text }); }, };

In the above code, the

ButtonActions.addNewItem
method will use
AppDispatcher
to dispatch the
ADD_NEW_ITEM
action to the Stores.

Dispatcher

The Dispatcher transfers the Actions to the Stores. It is essentially an event hub for your application's Views. There is only one global Dispatcher.

We use the Facebook official Dispatcher Library, and write a

AppDispatcher.js
as our application's dispatcher instance.

// dispatcher/AppDispatcher.js
var Dispatcher = require('flux').Dispatcher;
module.exports = new Dispatcher();

AppDispatcher.register()
is used for registering a callback for actions.
// dispatcher/AppDispatcher.js
var ListStore = require('../stores/ListStore');

AppDispatcher.register(function (action) { switch(action.actionType) { case 'ADD_NEW_ITEM': ListStore.addNewItemHandler(action.text); ListStore.emitChange(); break; default: // no op } })

In the above code, when receiving the

ADD_NEW_ITEM
action, the callback will operate the
ListStore
.

Please keep in mind, Dispatcher has no real intelligence on its own — it is a simple mechanism for distributing the actions to the stores.

Stores

The Stores contain the application state. Their role is somewhat similar to a model in a traditional MVC.

In this demo, we have a

ListStore
to store data.

// stores/ListStore.js
var ListStore = {
  items: [],

getAll: function() { return this.items; },

addNewItemHandler: function (text) { this.items.push(text); },

emitChange: function () { this.emit('change'); } };

module.exports = ListStore;

In the above code,

ListStore.items
is used for holding items,
ListStore.getAll()
for getting all these items, and
ListStore.emitChange()
for emitting an event to the Views.

The Stores should implement an event interface as well. Since after receiving an action from the Dispatcher, the Stores should emit a change event to tell the Views that a change to the data layer has occurred.

// stores/ListStore.js
var EventEmitter = require('events').EventEmitter;
var assign = require('object-assign');

var ListStore = assign({}, EventEmitter.prototype, { items: [],

getAll: function () { return this.items; },

addNewItemHandler: function (text) { this.items.push(text); },

emitChange: function () { this.emit('change'); },

addChangeListener: function(callback) { this.on('change', callback); },

removeChangeListener: function(callback) { this.removeListener('change', callback); } });

In the above code,

ListStore
inheritances
EventEmitter.prototype
, so you can use
ListStore.on()
and
ListStore.emit()
.

After updated(

this.addNewItemHandler()
), the Stores emit an event(
this.emitChange()
) declaring that their state has changed, so the Views may query the new state and update themselves.

Views, again

Now, we come back to the Views for implementing an callback for listening the Store's

change
event.
// components/MyButtonController.jsx
var React = require('react');
var ListStore = require('../stores/ListStore');
var ButtonActions = require('../actions/ButtonActions');
var MyButton = require('./MyButton');

var MyButtonController = React.createClass({ getInitialState: function () { return { items: ListStore.getAll() }; },

componentDidMount: function() { ListStore.addChangeListener(this._onChange); },

componentWillUnmount: function() { ListStore.removeChangeListener(this._onChange); },

_onChange: function () { this.setState({ items: ListStore.getAll() }); },

createNewItem: function (event) { ButtonActions.addNewItem('new item'); },

render: function() { return ; } });

In the above code, you could see when

MyButtonController
finds out the Store's
change
event occurred, it calls
this._onChange
to update the component's state, then trigger a re-render.
// components/MyButton.jsx
var React = require('react');

var MyButton = function(props) { var items = props.items; var itemHtml = items.map(function (listItem, i) { return

  • {listItem}
  • ; });

    return

      {itemHtml}
    New Item
    ; };

    module.exports = MyButton;

    License

    MIT

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