Just an example of handling view null checks in presenter in a low boilerplate, functional style with Kotlin (inline functions, extension functions, lambda arguments, etc)

PresenterViewRefInlineFuncs.kt

interface Presenter<V> {
  fun getView(): V
  fun attachView(view: V)
  fun detachView()
}

/*
  Functional style of handling view null-checking/handling
  
  Functions apply methods on the view, or pass view as argument to functions.
  There is "do-nothing" if view is detached, throw exception if view is detached, and 
  "do-something" (like analytics, or logging, etc.) if view is detached
*/

inline fun <V> Presenter<V>.onView(opOnView: V.() -> Unit) {
  getView()?.opOnView()
}

inline fun <V> Presenter<V>.onViewOrThrow(opOnView: V.() -> Unit, errorMsg: String? = null) {
  getView()?.opOnView() ?: throw Exception(errorMsg ?: "view is not attached")
}

inline fun <V> Presenter<V>.onView(opOnView: V.() -> Unit, actionWhenViewDetached: () -> Unit) {
  val view = getView()
  when (view) {
    null -> actionWhenViewDetached()
    else -> view.opOnView()
  }
}

inline fun <V> Presenter<V>.withView(withViewOp: (V) -> Unit) {
  val view = getView()
  if (view != null) withViewOp(view)
}

inline fun <V> Presenter<V>.withView(withViewOp: (V) -> Unit, actionWhenViewDetached: () -> Unit) {
  val view = getView()
  when (view) {
    null -> actionWhenViewDetached()
    else -> withViewOp(view)
  }
}

inline fun <V> Presenter<V>.withViewOrThrow(withViewOp: (V) -> Unit, errorMsg: String? = null) {
  val view = getView()
  when (view) {
    null -> throw Exception(errorMsg ?: "view is not attached")
    else -> withViewOp(view)
  }
}