Imagine walking through an art museum and finding two identical Mona Lisa paintings hanging on the wall. That situation would most likely cause a few raised eyebrows. Art museums should only contain unique content, like a set does in Swift.

A set is an unordered collection of unique elements.

There are many similarities between sets and arrays, but the main differences between the two are:

  • Set elements cannot be repeated, while that is allowed in arrays.
  • A set does not have a defined order, while an array does.

Sets are a great collection type to use when the data we need to store must be unique.

For example, we could use a set in real life to store information about employee ID numbers at a company or to store bank account numbers.

In this lesson, we will learn how to create and use sets in Swift.


Take a look at the image to the right.

When the unique item, "T" tries to join the group of letters, it is allowed in; however, when a second "S" attempts to join the set of letters, it is not allowed in because an "S" item already exists.

When you’re all set, click Next to continue.

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