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Enumerations aren’t technically one of the three primary collection types offered by Swift (Arrays, Sets, and Dictionaries). However, they do define a set of cases, and you may find yourself in a situation where it is convenient to iterate across all of the cases like you would with a collection. Let’s say that you are making an app where the user can select the season:

enum Season { case winter case spring case summer case fall }

We need to be able to iterate over all the seasons to show them in an array. Since enumerations aren’t able to do this on their own, we need to utilize a protocol. You’ll learn about protocols more in-depth later, but all you need to know now is that protocols define a set of methods and properties that can be adopted by an enumeration.

To iterate over the seasons, we’ll use the CaseIterable protocol. Here’s the syntax:

enum Season: CaseIterable { case winter case spring case summer case fall }

CaseIterable gives us access to a property called allCases that returns an array of case values. We’ll append this property onto Season and iterate over each case with a for loop:

for season in Season.allCases { print(season) } /* Prints to the console: winter spring summer fall */

Instructions

1.

Give the Vehicle enumeration access to all of the properties and methods of the CaseIterable protocol.

2.

Create a for loop that prints all of the cases of the Vehicle enum.

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