Implementation of generateWithTime from the Reactive Framework in Mathematica

RxInMathematica

ClearAll[generateWithTime, createObserver, observer, observable, 
  disposable, task];
generateWithTime[
   initialState_,
   condition_,
   resultSelector_,
   timeSelector_,
   iterate_] :=
  Module[{
    state = initialState,
    lastTaskForCleanup,
    runNextTask,
    observable = Unique[],
    disposed = False,
    disposable = Unique[]},
   observable["Subscribe"] = Function[observer,
     Module[{
       (* unpack the observer *)
       hasOnNext = ValueQ[observer["OnNext"]],
       OnNext = observer["OnNext"],
       hasOnCompleted = ValueQ[observer["OnCompleted"]],
       OnCompleted = observer["OnCompleted"],
       hasOnError = ValueQ[observer["OnError"]],
       OnError = observer["OnError"],
       defaultCatchResult = Unique[]
       },
      ClearAll[runNextTask];(* protect from asynch GC *)
      (* see http://mathematica.stackexchange.com/questions/3807/
      module-variable-scoping-in-scheduled-tasks *)
      If[Not[hasOnNext], Throw["Observer must have OnNext"]];
      runNextTask = Function[
        Module[{oldState = state, proceed, catchResult},
         (Quiet@RemoveScheduledTask@lastTaskForCleanup;
          catchResult = Catch[(* catch errors creating task *)
            lastTaskForCleanup =
             CreateScheduledTask[
              catchResult = Catch[
                proceed = condition[oldState];
                If[proceed && Not[disposed],
                 (OnNext[resultSelector[oldState]];
                  state = iterate[oldState];
                  runNextTask[]),
                 (Quiet@RemoveScheduledTask@lastTaskForCleanup;
                  If[hasOnCompleted, OnCompleted[]])];
                defaultCatchResult];(* end of catch *)
              If[(* catch errors in OnNext, proceed, iterat *)
               catchResult =!= defaultCatchResult && hasOnError,
               (OnError[catchResult];
                Quiet@RemoveScheduledTask@lastTaskForCleanup)],
              {timeSelector[oldState]}];
            defaultCatchResult];
          If[(* error in timeSelector *)
           catchResult =!= defaultCatchResult && hasOnError,
           (OnError[catchResult];
            Quiet@RemoveScheduledTask@lastTaskForCleanup),
           StartScheduledTask@lastTaskForCleanup]
          )(* End of Module internal to runNextTask *)
         ](* return value of runNextTask *)
        ]];(* end of def runNextTask *)
     runNextTask[];
     disposable["Dispose"] = Function[disposed = True];
     disposable
     ];(* end of def Subscribe *)
   observable
   ](* end of def generateWithTime *);
createObserver[onNext_, onCompleted_: False, onError_: False] :=
  Module[{o = Unique[]},
   o["OnNext"] = onNext;
   If[onCompleted =!= False, o["OnCompleted"] = onCompleted];
   If[onError =!= False, o["OnError"] = onError];
   o];
observable =
  generateWithTime[0,
   # < 3 &,
   If[# === 2, Throw[#], #] &,
   0.10 &,
   # + 1 &];
observer = createObserver[
   (* OnNext      *)Print["Rx ONNEXT: " <> ToString@#] &,
   (* OnCompleted *)Print["Rx DONE!"] &,
   (* OnError     *)Print["Rx ERROR: " <> ToString@#] &];
disposable = observable["Subscribe"][observer];
(*task=CreateScheduledTask[
(disposable["Dispose"][];
RemoveScheduledTask[task]),
{0.25}];
StartScheduledTask[task];*)

Print[ScheduledTasks[] // Length];
RemoveScheduledTask[ScheduledTasks[]]