Providing a delegate kotlin 1.1

SendingImagesResult.kt

class MyActivity : AppCompatActivity() {
    private val d: TextView by findRes(R.id.action_bar)

}

class ResourceLoader<out V>(val id: Int)  {

    private var cache : V? = null
    private var rootView: View? = null

    operator fun provideDelegate(
            thisRef: Activity,
            prop: KProperty<*>
    ) : ReadOnlyProperty<Activity, V> {

        return object : ReadOnlyProperty<Activity, V> {
            override fun getValue(thisRef: Activity, property: KProperty<*>): V {
                val currentRootView = thisRef.findViewById(android.R.id.content)
                val localCache = cache
                return when {
                    currentRootView != localCache || localCache == null -> {
                        (currentRootView.findViewById(id) as V).also {
                            cache = it
                            rootView = currentRootView
                        }
                    }
                    else -> localCache
                }
            }
        }
    }

}

fun <V: View> Activity.findRes(@IntegerRes id: Int) = ResourceLoader<V>(id)