@stalbert which numbers do you mean?

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