Swift Enumerations

In Swift, an Enumeration defines a common type for a group of related values and enables you to work with those values in a type-safe way within your code. Enumeration is a user-defined data type that consists of a set of named values, called members or cases.

Declaring an Enumeration

To declare an enumeration, you use the enum keyword followed by the name of the enumeration. Here's a simple example:

1enum Direction {
2    case north
3    case south
4    case east
5    case west
6}

In the above example, we declared an enumeration called Direction which contains four possible cases - north, south, east and west.

We can also declare an enumeration with all the cases in a single line separated by a comma:

1enum Day: String {
2    case monday, tuesday, wednesday, thursday, friday, saturday, sunday
3}

In the above example, we declared an enumeration called Day which contains seven possible cases - monday, tuesday, wednesday, thursday, friday, saturday, and sunday.

We can also associate values with enumeration cases:

1enum Planet: Int {
2    case mercury = 1, venus, earth, mars, jupiter, saturn, uranus, neptune
3}

In the above example, we declared an enumeration called Planet which contains eight possible cases, and we associated a raw value of type Int with each case.

Accessing Enumeration Values

You can access an enumeration value using the dot syntax. Here's an example:

1var dir = Direction.north
2dir = .south

In the above example, we assigned the Direction.north value to the dir variable, and then we assigned the Direction.south value to it.

We can also access the raw value of an enumeration case:

1let planet = Planet.jupiter
2print(planet.rawValue) // Output: 5

In the above example, we accessed the jupiter case of the Planet enumeration and printed its associated raw value, which is 5.

Switch Statements with Enumerations

Swift switch statements are very useful when working with enumerations. Here's an example:

1enum TrafficLight {
2    case red, yellow, green
3}
4
5var light = TrafficLight.red
6
7switch light {
8case .red:
9    print("Stop!")
10case .yellow:
11    print("Prepare to stop.")
12case .green:
13    print("Go!")
14}

In the above example, we declared an enumeration called TrafficLight with three cases - red, yellow, and green. We then assigned the TrafficLight.red value to the light variable and used a switch statement to determine what action to take based on the value of the light variable.

Iterating over Enumerations

You can also iterate over an enumeration to access its cases. Here's an example:

1enum Beverages: CaseIterable {
2    case coke, pepsi, fanta, sprite
3}
4
5for beverage in Beverages.allCases {
6    print(beverage)
7}

In the above example, we declared an enumeration called Beverages with four cases - coke, pepsi, fanta, and sprite. We then used the allCases property to iterate over the enumeration and print each case.