HashSet<E>.from constructor Null safety

  1. Iterable elements

Create a hash set containing all elements.

Creates a hash set as by HashSet<E>() and adds all given elements to the set. The elements are added in order. If elements contains two entries that are equal, but not identical, then the first one is the one in the resulting set.

All the elements should be instances of E. The elements iterable itself may have any element type, so this constructor can be used to down-cast a Set, for example as:

Set<SuperType> superSet = ...;
Set<SubType> subSet =


final numbers = <num>[10, 20, 30];
final hashSetFrom = HashSet<int>.from(numbers);
print(hashSetFrom); // fx {20, 10, 30}


factory HashSet.from(Iterable<dynamic> elements) {
  HashSet<E> result = HashSet<E>();
  for (final e in elements) {
    result.add(e as E);
  return result;