title: React / MobX: Store values are undefined?
body: <p>My MobX autorun function logs out <code>undefined</code> for both of the values here. Also, in my components that <code>import user from '../../stores/UserStore</code>, the instances that I use <code>{user.userName}</code> all show nothing at all.</p>
  
  <pre><code>import { observable, autorun } from 'mobx'
  
  class UserStore {
    @observable userName = "tommy";
    @observable arr = [0,1]
  }
  
  const user = window.user = new UserStore
  
  export default user;
  
  
  // user.userName = "timmy"; // works, but not observable.
  
  autorun(() =&gt; {
    console.log(user.userName) // undefined
    console.log(user.arr) // undefined
  })
  </code></pre>