CODESAMPLE

Iterator - Dart

Iterator Dart

The Iterator pattern provides a way to access the elements of an aggregate object sequentially without exposing its underlying representation. It defines a standard interface for creating iterators and iterating over collections. This implementation uses Dart’s Iterable and Iterator classes. The Album class represents the aggregate, and the AlbumIterator class provides the iteration logic. Dart’s yield keyword makes creating iterators concise, and using an Iterable allows the Album class to be used with other Dart collection utilities easily. This embraces the functional aspects of Dart and utilizes its built-in iteration support.

// Define the iterator class
class AlbumIterator<T> implements Iterator<T> {
  final List<T> _data;
  int _currentIndex = 0;

  AlbumIterator(this._data);

  @override
  T get current => _data[_currentIndex];

  @override
  bool moveNext() {
    return _currentIndex < _data.length - 1;
  }
}

// Define the aggregate class (collection)
class Album<T> extends Iterable<T> {
  final List<T> _songs;

  Album(this._songs);

  @override
  Iterator<T> get iterator => AlbumIterator(_songs);

  void addSong(T song) {
    _songs.add(song);
  }
}

void main() {
  final album = Album<String>(['Song 1', 'Song 2', 'Song 3']);

  for (final song in album) {
    print(song);
  }

  final iterator = album.iterator;
  while (iterator.moveNext()) {
    print('Current song using iterator: ${iterator.current}');
  }
}