Dart Streams Example with a Cake Factory

stream.dart

import 'dart:async';

class Cake {}

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

void main() {
  final controller = StreamController();

  final order = Order('chocolate');

  // create baker to bake the order
  final baker = StreamTransformer.fromHandlers(handleData: (cakeType, sink) {
    if (cakeType == 'chocolate') {
      sink.add(Cake());
    } else {
      sink.addError("I can't bake that type!");
    }
  });

  controller.sink.add(order);

  controller.stream
      // create order inspector
      // order inspector recieves an order object
      // hands of a string to the baker.
      // return the type of order
      .map((order) => order.type)
      // connect baker to stream
      .transform(baker)
      // add pickup office
      // listens to any value coming out of the stream.
      .listen((cake) => {print("Here's your $cake")},
          onError: (error) => {print(error)});
}