Learn
Sets
Review

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.