Introduction to Swift Enums

Swift Enums (Enumerations) are a powerful and flexible way to define a group of related values in a type-safe manner. They allow you to organize your code and represent data with distinct cases, making your code more readable and maintainable.

Defining an Enum

To create an enum, you define it with the enum keyword followed by the name and a list of cases. Each case represents a distinct value the enum can hold.

enum Direction {
    case north
    case south
    case east
    case west
}

Using Enums

Accessing Enum Cases

You can access the individual cases of an enum using dot notation:

let myDirection = Direction.north
print(myDirection) // Output: north

Switch Statements with Enums

Switch statements are particularly useful with enums to handle different cases:

let userChoice = Direction.east

switch userChoice {
case .north:
    print("Heading North")
case .south:
    print("Heading South")
case .east:
    print("Heading East")
case .west:
    print("Heading West")
}

Associated Values

Enums can hold associated values, allowing them to carry additional data:

enum Weather {
    case sunny
    case rainy(Int) // The associated value is the rainfall in millimeters
    case cloudy(WeatherType) // The associated value is another enum
}

enum WeatherType {
    case cumulus
    case stratus
    case cirrus
}

let todayWeather = Weather.rainy(15)

Raw Values

You can assign raw values of the same type to each case, enabling easy conversion between raw values and enum values:

enum DayOfWeek: Int {
    case sunday = 1
    case monday
    case tuesday
    case wednesday
    case thursday
    case friday
    case saturday
}

let today = DayOfWeek.wednesday
print(today.rawValue) // Output: 4

Enum Methods and Properties

You can also add methods and properties to enums, just like with other Swift types:

enum TrafficLight {
    case red
    case yellow
    case green

    var description: String {
        switch self {
        case .red:
            return "Stop"
        case .yellow:
            return "Prepare to go"
        case .green:
            return "Go"
        }
    }
}

let currentLight = TrafficLight.green
print(currentLight.description) // Output: "Go"