Kotlin watch array change

Question

I'm trying to be notified when an array changes its content. Through this code I'm able to notify the setting of the array, but nothing happens when a new item is inserted.

var array: MutableMap<String, List<String>> = mutableMapOf()
    set(value) {
        field = value
        arrayListener?.notify()
    }

The only thing I came up with is resetting the array to itself everytime I add, delete o edit items, like this:

array = array

I read this question How to watch for array changes? relative to Javascript, but I'd like an easier solution then creating a new object, can anyone suggest it?

Answer 1

Array's API is quite simple: elements can be written there and can be read from an array.

At 99% (a number without justification, read "the vast majority") array's usages people are satisfied with this simple API. It would be a shame if a simple interface with straightforward implementation was mixed with tricky functionality.

Moving to your problem, a possible approach could be create an array's wrapper

class ArrayWrapper<T> (private val array: Array<out T>, 
                       private val onChange: () -> Unit) {
    val size = array.size

    fun get(index: Int): T {
        return array[index]
    }

    fun set(index: Int, value: T) {
        array[index] = value
        onChange()
    }
}

An example of usage:

val ints = ArrayWrapper(arrayOf(1, 2, 3)) {
    println("Array has been changed")
}