on
also do an action, if Fetch is finished.
inline fun <T : Any> Fetch<T>.onFinished(predicate: Boolean, action: Fetch.Finished<T>.() -> Unit): Fetch<T>
inline fun <T : Any> Fetch<T>.onFinished(predicate: (result: T) -> Boolean, action: (T) -> Unit): Fetch<T>
also do an action, if predicate is true and Fetch is finished.