Stream example

Cake.dart

import 'dart:async';

class Cake {}
class Order {
  String type;
  Order(this.type);
}

void main() {
  final StreamController<Order> controller = new StreamController();
  
  
  final Order cakeOrder = new Order('chocolate');
  final Order cakeOrder2 = new Order('vanilla');
  
  final StreamTransformer<String, Cake> baker = new StreamTransformer.fromHandlers(
  	handleData: (String cakeType, EventSink<Cake> sink) {
      if (cakeType == 'chocolate') {
        sink.add(new Cake());
      } else {
        sink.addError('I only bake chocoalte cakes. I cannot bake your cake type!');
      }
    }
  );
  
  controller.sink.add(cakeOrder);
  controller.sink.add(cakeOrder2);
  
  controller.stream
    .map((Order o) => o.type)
    .transform(baker)
    .listen(
    	(cake) => print("Here is your cake! $cake"),
    	onError: (error) => print(error),
			onDone: () => print("all done!")
  	);
  
  controller.sink.close();
  
}