[dart:async] StreamTransformer Basic Usage

main.dart

import 'dart:async';

main() {
  StreamTransformer transformer = StreamTransformer<num, num>.fromHandlers(
    handleData: (num val, EventSink sink) {
      sink.add(val + 1);
    }
  );
  StreamController controller = StreamController<num>();
  Stream transformed = controller.stream.transform(transformer);
  
  transformed.listen((val) {
    print('Transformed event received: $val');
  }, onDone: () {
    print('Transformed stream done');
  });
  
  for (var i = 0; i < 10; i++) {
  	controller.sink.add(i);
  }
  
  controller.close();
}