Dart.Language.Extentions

main.dart

void main() {
  for (final current in StringIterable('Hello World!')) {
    print(current);
  }

//   for (final current in 'Hello World!'.toIterable()) {
//     print(current);
//   }
}

extension MyStringExtensions on String {
  StringIterable toIterable() {
    return StringIterable(this);
  }
}

class StringIterable extends Iterable<String> {
  StringIterable(this.source);

  final String source;

  @override
  Iterator<String> get iterator => StringIterator(source);
}

class StringIterator implements Iterator<String> {
  StringIterator(this.source);
  final String source;

  String _current;
  int _startIndex = 0;

  @override
  String get current => _current;

  @override
  bool moveNext() {
    if (_startIndex == source.length) {
      _current = null;
      return false;
    }

    _current = source.substring(_startIndex, _startIndex + 1);
    _startIndex++;
    return true;
  }
}

// abstract class Iterable<T> {
//   @override
//   Iterator<T> iterator;
// }

// abstract class Iterator<T> {
//   T get current;
//   bool moveNext();
// }