EventEmiter pausing and restarting - dart

Question

I have the following code
.html
<input
type = "text"
#raceCtrl = "ngForm"
[ngFormControl] = "raceForm.controls['raceCtrl']"
[(ngModel)] = "race.race"
(input) = "inputHandler()"
(mousemove) = "inputHandler()"
class = "mdl-textfield__input"
id = "race">
<input
type = "text"
#ethnicGroupCtrl = "ngForm"
[ngFormControl] = "raceForm.controls['ethnicGroupCtrl']"
[(ngModel)] = "race.ethnicGroup"
(input) = "inputHandler()"
(mousemove) = "inputHandler()"
class = "mdl-textfield__input"
id = "ethnicGroup">
.dart
RaceComponent( FormBuilder fb, ModelService modelSrvc ) {
raceForm = fb.group( {
'raceCtrl': ['', CustomValidators.requiredNounValidator( 2 )],
'ethnicGroupCtrl': ['', CustomValidators.optionalNounValidator( 2 )]
} );
_raceCtrl = raceForm.controls['raceCtrl'];
race = modelSrvc.getRace( );
inputHandler( );
}
void inputHandler( ) {
if ( raceForm.valid &&
!isEmpty( _raceCtrl.value ) ) {
isFormValid = true;
}
else {
isFormValid = false;
}
race.isValid = isFormValid;
}
onSubmit( ) {
isSubmitted = true;
if ( isFormValid ) {
raceEmitter.emit( {'topic': topic, 'race': race} );
}
else {
raceEmitter.emit( {'topic': topic, 'race': new Race( )} );
}
raceMap = new JsonObject.fromJsonString( encode( race ) );
The form submits as expected. But from then onwards the stream remains open and even when ethinicGroup has errors the error is propagated by the stream to storage. Is it possible to pause and unpause the stream depending on the validity of the form to prevent the erroneous data from being propagated.