Flutter : stream two Streams into a single screen?

Question

I have two streams fetching from two different api.

Stream<Month> get monthOutStream => monthOutController.stream; Stream<MySchedule> get resultOutStream => resultController.stream; 

I am fetching these data at two different state of the application, result at the begining and Months after some events from user.

MyScheduleBloc(){   initialData(); }  Future initialData() async {   MySchedule mySchedule = await myScheduleViewModel.importMySchedule(now.id);   resultController.add(mySchedule); } 

My screen has a streambuilder as

Widget build(BuildContext context) { final webCalenderBloc = WebCalenderBloc(); return StreamBuilder(   stream: webCalenderBloc.resultOutStream,   builder: (BuildContext context , snapdata){     if(!snapdata.hasData){       return Center(         child: CircularProgressIndicator(),       );     }     return body(snapdata.data);    },  ); } 

Since the main widget build method took the StreamBuilder Widget with resultoutstream as a stream.Where do i fetch the other stream monthoutStream. Can i fetch stream inside a stream? Do i missing anything while handling two stream.I dont want to build any widget from monthoutstream but want to check the data inside it.

Answer 1

You can nest StreamBuilder if needed. Nothing prevents you from doing the following:

StreamBuilder(   stream: stream1,   builder: (context, snapshot1) {     return StreamBuilder(       stream: stream2,       builder: (context, snapshot2) {         // do some stuff with both streams here       },     );   }, ) 

Another solution if this makes sense for you is: Streams are designed to be mergeable/transformed. You could make a third stream that is a merge of the two later streams.

Ideally for complex stream operations you'll want to use rxdart as it provides a few useful transformer.

Using rxdart, the fusion of two Observable (which are subclass of Stream) would be the following:

Observable<bool> stream1; Observable<String> stream2;  final fusion = stream1.withLatestFrom(stream2, (foo, bar) {   return MyClass(foo: foo, bar: bar); }); 

Answer 2

Observable.combineLatest2(         aStream,         bStream,         (a, b, c) =>         a != '' && b != ''); 

combineLatestN returns a combined stream