``` fun <V : View> Activity.bindOptionalView...

# announcements

[ursus]

fun <V : View> Activity.bindOptionalView(id: Int)
        : ReadOnlyProperty<Activity, V?> = optional(id, viewFinder)

fun <T, V : View> optional(id: Int, finder: T.(Int) -> View?)
        = Lazy { t: T, desc ->  t.finder(id) as V? }

private class Lazy<T, V>(private val initializer: (T, KProperty<*>) -> V) : ReadOnlyProperty<T, V> {
    private object EMPTY
    private var value: Any? = EMPTY

    override fun getValue(thisRef: T, property: KProperty<*>): V {
        if (value == EMPTY) {
            value = initializer(thisRef, property)
        }
        @Suppress("UNCHECKED_CAST")
        return value as V
    }
}