Step 1 - map

import 'dart:async';

Future<void> main() async {
  final s = Stream.fromIterable([1, 2, 3]).map((n) => 'n=$n');
  await for (final v in s) {
    print(v);
  }
}

Step 2 - where

import 'dart:async';

Future<void> main() async {
  final s = Stream.fromIterable([1, 2, 3, 4]).where((n) => n.isEven);
  print(await s.toList());
}

Step 3 - Chaining

import 'dart:async';

Future<void> main() async {
  final out = Stream.fromIterable([1, 2, 3, 4])
      .where((n) => n.isOdd)
      .map((n) => n * 10);
  await for (final v in out) {
    print(v);
  }
}

Good habit

• Transforms are lazy: nothing runs until someone listens or pulls with await for.

Practice tasks

• Add distinct() from package:async in a real project, or implement a tiny distinct extension that tracks the last value (optional).
• Build Stream<String> from ints with map and filter empty strings with where.