Why adding data in Flutter Sink is not working? - flutter

Question

Purpose is very simple. After getting data it is filterable by specific set of Strings. So I am initially filtering with 'all' which means showing all data and when clicking any choice chips then filtering based on that specific strings. Everything working fine except not showing all data after loading it from api call. Even if I Hot Reload again its showing the full list data. So basically adding string data in Sink is not working. I think I have done some silly mistake but couldn't figure it out. Need suggestions.
BLOC Class
final Application _application;
ProductListScreenBloc(this._application);
int totalPages = 1;
final _productList = BehaviorSubject<List<Product>>();
Observable<List<Product>> _filteredProductList = Observable.empty();
final _filterName = BehaviorSubject<String>();
Stream<List<Product>> get productList => _productList.stream;
Stream<List<Product>> get filteredProductList => _filteredProductList;
Sink<String> get filterName => _filterName;
void loadBrandWiseProductList(
String categorySlug, String brandSlug, int pageNo) {
if (totalPages >= pageNo) { //for pagination
StreamSubscription subscription = _application.productListRepository
.getBrandWiseProductList(categorySlug, brandSlug, pageNo)
.listen((ProductListResponse response) {
if (_productList.value == null) {
totalPages = response.totalPage;
_productList.add(response.productList);
filterName.add('all');
_filteredProductList = Observable.combineLatest2(
_filterName, _productList, applyModelFilter)
.asBroadcastStream();
}
});
}
}
List<Product> applyModelFilter(
String filter,
List<Product> products,
) {
if (filter == 'all') {
return products;
} else {
return products
.where((seriesSLug) => seriesSLug.series.slug == filter)
.toList();
}
}
UI Widget Class
class _AllSeriesModelListScreenState extends State<AllSeriesModelListScreen> {
AllSeriesModelListScreenArguments allSeriesModelListScreenArguments;
ProductListScreenBloc bloc;
int _selectedSeriesChipValue = -1;
int _pageNo = 1;
#override
void initState() {
super.initState();
}
#override
void dispose() {
super.dispose();
bloc.dispose();
}
#override
Widget build(BuildContext context) {
RouteSettings settings = ModalRoute.of(context).settings;
allSeriesModelListScreenArguments = settings.arguments;
_init();
return Scaffold(
body: CustomScrollView(
slivers: <Widget>[
StreamBuilder(
stream: bloc.filteredProductList,
builder: (context, snapshot) {
if (snapshot.hasData) {
List<Product> productList = snapshot.data;
return SliverPadding(
padding: EdgeInsets.symmetric(
vertical: 8.0,
horizontal: 10.0,
),
sliver: SliverGrid(
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 3,
crossAxisSpacing: 0.0,
mainAxisSpacing: 8.0,
),
delegate: SliverChildListDelegate(
buildModelGridList(productList),
),
),
);
} else {
return SliverList(
delegate: SliverChildListDelegate([
PaddingWithTitle(
title: 'No Model Available',
),
]),
);
}
})
],
),
);
}
void _init() {
if (null == bloc) {
bloc = ProductListScreenBloc(
AppProvider.getApplication(context),
);
bloc.loadBrandWiseProductList(
allSeriesModelListScreenArguments.categorySlug,
allSeriesModelListScreenArguments.brandSlug,
_pageNo);
}
}
}

Answer 1

I believe you have missed something in these 2 lines.
final _filterName = BehaviorSubject<String>();
Sink<String> get filterName => _filterName;
You are not exposing the sink. BehaviorSubject is just a StreamController with default value and cache for last value. So as every Stream controller it has 2 props - sink and stream. to push data you need to access the sink.
To do that you need to type
StreamSink<String> get filterName => _filterName.sink;
Plus why you do not have a seed value in the behavior subject?
It is required to have that "default" value
final _filterName = BehaviorSubject<String>(seedValue: '');

Answer 2

Just had to change the code into this
void loadBrandWiseProductList(
String categorySlug, String brandSlug, int pageNo) {
if (totalPages >= pageNo) { //for pagination
StreamSubscription subscription = _application.productListRepository
.getBrandWiseProductList(categorySlug, brandSlug, pageNo)
.listen((ProductListResponse response) {
if (_productList.value == null) {
totalPages = response.totalPage;
_productList.add(response.productList);
}
_filteredProductList = Observable.combineLatest2(
_filterName, _productList, applyModelFilter)
.asBroadcastStream();
});
}
}