title: Observable array in Kotlin to know when an array elt value is changed
body: <p>My goal: I have a simple class with a public </p>
  
  <pre><code>val reds = IntArray(10)
  val greens = IntArray(10)
  val blues = IntArray(10)
  val lums = IntArray(10)
  </code></pre>
  
  <p>If someone modifies <strong>any</strong> red value, I'd like to update the lum value.  </p>
  
  <pre><code>myObj.reds[5] = 100 // Should update myObj.lums[5] = reds[5]+greens[5]+blues[5]
  </code></pre>
  
  <p>The problems is that the <code>by Delegates.observable</code> seem to only be used for var objects - nothing mentions "and if you modify an element of an array, here is what gets triggered"</p>
  
  <p>Maybe this isn't possible and I have to do all modifications through getters and setters - but I'd much rather have something trigger like an observable!</p>