Another set operation we can use is .union(). This operation creates a set by combining the values of two sets together.

The syntax for creating a set using .union() is:

var NewSet = SetA.union(SetB)

Consider the following sets book1 and book2 that contain the characters of different fairy tales:

var book1: Set = ["Pig 1", "Pig 2", "Pig 3", "Wolf"]

var book2: Set = ["Little Red Riding Hood", "Grandma", "Wolf"]

We can use .union() to combine all the characters into one set called fairyTales:

var fairyTales = book1.union(book2)

Imagine finding a third book, book3:

var book3: Set = ["Jack", "Blunderbore", "Beanstock"]

With set operations, we can combine multiple sets like this:

var fairyTales = book1.union(book2).union(book3)

Using multiple methods in the same line of code is known as method chaining.

When we print fairyTales, we will get something similar to the following output:

["Blunderbore", "Pig 1", "Pig 2", "Little Red Riding Hood", "Pig 3", "Grandma", "Wolf", "Jack", "Beanstock"]

The element "Wolf" appeared in both book1 and book2; however, the element only appears once in fairyTales because sets only contain unique elements.