Great job completing this lesson!

Let’s go over what we learned:

A set is an unordered collection of unique elements.

We have the option to initialize sets that are either empty or populated:

var emptySet = Set<Type>() var populatedSet: Set = [Value1, Value2, Value3]To add new elements to a set, use the built-in method,

`.insert(Value)`

.We can remove a single element from a set using

`.remove(Value)`

or we can remove all the values from a set with`.removeAll()`

:If we want to check if a value exists within a set, we can use the method

`.contains(Value)`

.A

`for`

-`in`

loop can be used to iterate through all the values of a set:for placeholder in setName { // Body of loop }We can use set operations to modify or create new sets based on the data in two different sets.

The

`.intersection()`

operation creates sets with values that overlap in two sets:soda.intersection(seltzer)The

`.union()`

operation combines all the values of two different sets:ketchup.union(mayo)The operation

`.symmetricDifference()`

creates a set of items that appear in one set, but not both:capulets.symmetricDifference(montagues)`.subtracting()`

is a set operation that removes the overlapping data of one set from another:milkshake.subtracting(iceCream)

### Instructions

Feel free to use the space in **Review.swift** to practice using sets.

When you’re ready to move on, click **Up Next**.