ListMap<K, V>.fromEntries constructor

ListMap<K, V>.fromEntries(Iterable<MapEntry<K, V>> entries, { bool sort = false, int compare(K a, K b)?, })

Creates a ListMap from entries. If entries contains the same keys multiple times, the last occurrence overwrites the previous value.

If sort is true, the entries will be sorted with compare, if provided, or with compareObject if not provided. If sort is false, compare will be ignored.

Implementation

factory ListMap.fromEntries(
  Iterable<MapEntry<K, V>> entries, {
  bool sort = false,
  int Function(K a, K b)? compare,
}) {
  assert(compare == null || sort == true);

  Map<K, V> map;
  List<K> list;

  // Sorted:
  if (sort) {
    map = HashMap<K, V>();
    for (final MapEntry<K, V> entry in entries) {
      map[entry.key] = entry.value;
    }
    list = map.entries.map((entry) => entry.key).toList(growable: false);
    list.sort(compare ?? compareObject);
  }
  // Insertion order:
  else {
    // First create a map in insertion order, removing duplicate keys.
    map = LinkedHashMap<K, V>.fromEntries(entries);

    // Then create the list in the insertion order.
    list = map.entries.map((entry) => entry.key).toList(growable: false);

    // Remove the linked-list from the map (by using a HashMap).
    map = HashMap.of(map);
  }

  return ListMap._(map, list);
}