groupFoldBy<K, G> method

*<Null safety>*

Map<K, G> groupFoldBy <K, G>(K keyOf(T element), G combine(G? previous, T element))

Implementation

Map<K, G> groupFoldBy<K, G>(
    K Function(T element) keyOf, G Function(G? previous, T element) combine) {
  var result = <K, G>{};
  for (var element in this) {
    var key = keyOf(element);
    result[key] = combine(result[key], element);
  }
  return result;
}