union method

Set<E> union(Set<E> other)

Returns a new set which contains all the elements of this set and other.

That is, the returned set contains all the elements of this Set and all the elements of other.

Source

Set<E> union(Set<E> other) {
  return toSet()..addAll(other);
}

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Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/1.24.3/dart-collection/SetMixin/union.html