Mobx: add new (array) property to observable object
<p>I have an observable object, where I want to store some data.
Keys are unique IDs for my customer entity, and values are arrays of customers' orders (which are objects themselves).</p>

<p>I initialize an object with:</p>

<pre><code>@observable data =  {};
</code></pre>

<p>Then, when I get data from network, I want to store them, using:</p>

<pre><code>@action
saveData(customerId, ordersForCustomer) {
  this.data = extendObservable(this.data, {
    [customerId]: observable(ordersForCustomer);
  }
}
</code></pre>

<p>Unfortunately, it seems my object (or its properties) are not being watched.</p>

<p>Why is this? And how can I fix this? Is there something special I need to know about how observable objects work with arrays as its values?</p>