Reduce boilerplates for operator == and hashCode

main.dart

/// Generates a hash code for multiple [objects].
int hashValues(Iterable objects) => _finish(
    objects.fold(0, (hash, element) => _combine(hash, element.hashCode)));

// Jenkins hash functions
int _combine(int hash, int value) {
  hash = 0x1fffffff & (hash + value);
  hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10));
  return hash ^ (hash >> 6);
}

int _finish(int hash) {
  hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
  hash = hash ^ (hash >> 11);
  return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
}

class Item {
  final String id;
  final String title;
  final int numberOfparts;
  final double weight;
  final bool composable;

  const Item({
    this.id,
    this.title,
    this.numberOfparts,
    this.weight,
    this.composable,
  });

  @override
  bool operator ==(dynamic other) =>
      identical(other, this) ||
      other.id == id &&
          other.title == title &&
          other.numberOfparts == numberOfparts &&
          other.weight == weight &&
          other.composable == composable;

  @override
  int get hashCode =>
      hashValues([id, title, numberOfparts, weight, composable]);
}

void main() {
  final item1 = Item(
      id: '1',
      title: 'Item 1',
      numberOfparts: 5,
      weight: 10.45,
      composable: true);

  final item2 = Item(
      id: '1',
      title: 'Item 1',
      numberOfparts: 5,
      weight: 10.45,
      composable: true);

  item1 == item2 ? print('Equal') : print('Not Equal');
}