How to connect state to props with mobx.js @observer when use ES6 class?

Question

Let's take a class like this in an app with React and React Router.

@observer class Module1 extends React.Component {

  constructor (props) {
    super(props);
    //...
  }

  componentWillMount(){
    //...
  }

  method(){
    //...
  }

  otherMethod(){
    //...
  }

  render() {
    return (
       <ChildComp bars={this.props.bars}/>}
    );
  }
}

And let's take a state like this

state = observable({
  module1:{
    bars:{
      //...
    }
  },
  module2:{
    foos:{
      //...
    }
  }
})

The Module1 component is loaded like this:

//index.js
render(
      <Router history={browserHistory}>
        <Route path="/" component={App}>
          <Route path='/map' component={Module1} >
            <Route path="/entity/:id" component={SubModule}/>
          </Route>
          <Route path='/map' component={Module2} >
        </Route>
      </Router>,
      document.getElementById('render-target')
    );

How could I pass the props module1.bars to Module1 component? In redux I would use <provider>and redux-connect but I am a bit lost with this in Mobx.js.

Answer 1

One week ago we started a new project with with react and mobx, and I faced the same issue as yours. After looking around I found the best way is to use react's context. Here's how:

The store: stores/Auth.js

import { get, post } from 'axios';
import { observable, computed } from 'mobx';
import jwt from 'jsonwebtoken';
import singleton from 'singleton';

import Storage from '../services/Storage';

class Auth extends singleton {
  @observable user = null;
  @computed get isLoggedIn() {
    return !!this.user;
  }

  constructor() {
    super();

    const token = Storage.get('token');

    if (token) {
      this.user = jwt.verify(token, JWT_SECRET);
    }
  }

  login(username, password) {
    return post('/api/auth/login', {
      username, password
    })
    .then((res) => {
      this.user = res.data.user;
      Storage.set('token', res.data.token);
      return res;
    });
  }

  logout() {
    Storage.remove('token');
    return get('/api/auth/logout');
  }
}

export default Auth.get();

Note: we are using singleton to make sure that it's one instance only, because the store can be used outside react components, eg. routes.js

The routes: routes.js

import React from 'react';
import { Route, IndexRoute } from 'react-router';

import App from './App';
import Login from './Login/Login';
import Admin from './Admin/Admin';
import Dashboard from './Admin/views/Dashboard';
import Auth from './stores/Auth'; // note: we can use the same store here..

function authRequired(nextState, replace) {
  if (!Auth.isLoggedIn) {
    replace('/login');
  }
}

export default (
  <Route name="root" path="/" component={App}>
    <Route name="login" path="login" component={Login} />
    <Route name="admin" path="admin" onEnter={authRequired} component={Admin}>
      <IndexRoute name="dashboard" component={Dashboard} />
    </Route>
  </Route>
);

The main component: App.js

// App.js
import React, { Component } from 'react';
import Auth from './stores/Auth';

export default class App extends Component {

  static contextTypes = {
    router: React.PropTypes.object.isRequired
  };

  static childContextTypes = {
    store: React.PropTypes.object
  };

  getChildContext() {
    /**
     * Register stores to be passed down to components
     */
    return {
      store: {
        auth: Auth
      }
    };
  }

  componentWillMount() {
    if (!Auth.isLoggedIn) {
      this.context.router.push('/login');
    }
  }

  render() {
    return this.props.children;
  }
}

And finally, a component using the store: Login.js

import React, { Component } from 'react';
import { observer } from 'mobx-react';

@observer
export default class Login extends Component {

  static contextTypes = {
    router: React.PropTypes.object.isRequired,
    store: React.PropTypes.object.isRequired
  };

  onSubmit(e) {
    const { auth } = this.context.store; // this is our 'Auth' store, same observable instance used by the `routes.js`

    auth.login(this.refs.username.value, this.refs.password.value)
      .then(() => {
        if (auth.isLoggedIn) this.context.router.push('/admin');
      })
      .catch((err) => {
        console.log(err);
      });

    e.preventDefault();
  }

  render() {
    return (
      <div className="login__form">
        <h2>Login</h2>
        <form onSubmit={this.onSubmit.bind(this)}>
          <input type="text" ref="username" name="username" placeholder="Username" />
          <input type="password" ref="password" name="password" placeholder="Password" />
          <button type="submit">Login</button>
        </form>
      </div>
    );
  }
}

You can declare new stores and add them in getChildContext of App.js, and whenever you need a certain store just declare the store dependency in the component's contextTypes, and get it from this.context.

I noticed that it's not a requirement to pass an observable as prop, just by having the @observer decorator and using any observable value in your component, mobx and mobx-react do their magic.

By the way redux's <Provider store={myStore}><App /></Provider> does the same thing as explained in App.js. https://egghead.io/lessons/javascript-redux-passing-the-store-down-implicitly-via-context

Reference:

• http://mobxjs.github.io/mobx/refguide/observer-component.html
• https://facebook.github.io/react/docs/context.html