RxCommandListener.dart

   RxCommandListener<ImageStorageRequest, ImageLocation> selectImageListener;
  RxCommandListener<ChatEntry, void> deleteChatEntryListener;

  @override
  void initState() {
    super.initState();

    selectImageListener = RxCommandListener(
        command: sl.get<ImageManager>().selectAndUploadImageCommand,
        onValue: (imageLocation) async {
          if (imageLocation == null) return;

          sl.get<EventManager>().createChatEntryCommand(new ChatEntry(
                event: widget.event,
                isImage: true,
                content: imageLocation.downloadUrl,
              ));
        },
        onIsBusy: () => JoCLoader.show(context),
        onNotBusy: JoCLoader.hide,
        onError: (ex) => showMessageDialog(context, 'Upload problem',
            "We cannot upload your selected image at the moment. Please check your internet connection"));

    deleteChatEntryListener = RxCommandListener(
      command: sl.get<EventManager>().deleteChatEntryCommand,
      onValue: (_) => setState(() => {}),
    );

  void dispose() {
    selectImageListener?.dispose();
    deleteChatEntryListener?.dispose();
  }



////////////////////////////////////////////////////////
//compared to:
///////////////////////////////////////////////////////

StreamSubscription deleteChatEntrySubscription;
  StreamSubscription _selectImageIsExecutingSubscription;
  StreamSubscription _selectImageCommandSubscription;
  StreamSubscription _selectImageErrorSubscription;

  

  @override
  void initState() {
    super.initState();

    _selectImageCommandSubscription = sl
        .get<ImageManager>()
        .selectAndUploadImageCommand
        .listen((imageLocation) async {
      if (imageLocation == null) return;

      sl.get<EventManager>().createChatEntryCommand(new ChatEntry(
            event: widget.event,
            isImage: true,
            content: imageLocation.downloadUrl,
          ));
    });

    _selectImageIsExecutingSubscription = sl
        .get<ImageManager>()
        .selectAndUploadImageCommand
        .isExecuting
        .listen((busy) {
      if (busy) {
        JoCLoader.show(context);
      } else {
        JoCLoader.hide();
      }
    });

    _selectImageErrorSubscription = sl
        .get<ImageManager>()
        .selectAndUploadImageCommand
        .thrownExceptions
        .listen((ex) => showMessageDialog(context, 'Upload problem',
            "We cannot upload your selected image at the moment. Please check your internet connection"));

    deleteChatEntrySubscription = sl
        .get<EventManager>()
        .deleteChatEntryCommand
        .listen((_) => setState(() => {}));
  }

 void dispose() {
    _selectImageIsExecutingSubscription?.cancel();
    _selectImageCommandSubscription?.cancel();
    _selectImageErrorSubscription?.cancel();
    deleteChatEntrySubscription?.cancel();
 }

This is the definition of an RxCommandListener

class RxCommandListener<TParam, TResult> {
  StreamSubscription valueSubscription;
  StreamSubscription resultsSubscription;
  StreamSubscription busyChangeSubscription;
  StreamSubscription busySubscription;
  StreamSubscription errorSubscription;
  StreamSubscription canExecuteStateSubscription;

  final RxCommand<TParam, TResult> command;

  final void Function(TResult value) onValue;
  final void Function(bool isBusy) onIsBusyChange;
  final void Function(Exception ex) onError;
  final void Function(bool state) onCanExecuteChange;
  final void Function(CommandResult<TResult> result) onResult;
  final void Function() onIsBusy;
  final void Function() onNotBusy;

  final Duration debounceDuration;

  RxCommandListener({
    @required
    this.command,
    this.onValue,
    this.onIsBusyChange,
    this.onIsBusy,
    this.onNotBusy,
    this.onError,
    this.onCanExecuteChange,
    this.onResult,
    this.debounceDuration,}
  )