.union()

The .union() method returns a new set containing all elements of one set combined with the elements of a given set.

firstSet.union(secondSet)

Sets firstSet and secondSet must have countable number of members.

let friends: Set = ["Pam", "Jim", "Andy", "Darryl"]
let colleagues = ["Dwight", "Michael", "Ed"]
let friendsAndColleagues = friends.union(colleagues)
print(friendsAndColleagues)

let luckyNumbers: Set = [12, 13]
let luckySequence = (4...8)
let goodNumbers = luckyNumbers.union(luckySequence)
print(goodNumbers)

This will output:

["Darryl", "Pam", "Jim", "Ed", "Andy", "Michael", "Dwight"]
[12, 4, 5, 6, 7, 8, 13]

Note: A set is an unordered data structure, so output elements may be ordered differently.