Enumerations

Declaring Enums

Enums are declared using the enum keyword followed by the enumeration name and a set of cases enclosed in curly braces.

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

Using Enums

Once an enum is declared, you can create a variable of that enum type and assign it one of the enum cases.

var currentDirection: Direction = .north

Switch Statement with Enums

Enums work exceptionally well with switch statements, allowing you to handle each case concisely.

switch currentDirection {
case .north:
    print("Heading north")
case .south:
    print("Heading south")
case .east:
    print("Heading east")
case .west:
    print("Heading west")
}

Associated Values

Swift enums can store associated values, allowing you to attach additional information to each case.

enum Barcode {
    case upc(Int, Int, Int, Int)
    case qrCode(String)
}

Using Associated Values

You can extract the associated values as part of a switch statement.

let productBarcode = Barcode.upc(8, 85909, 51226, 3)
 
switch productBarcode {
case .upc(let numberSystem, let manufacturer, let product, let check):
    print("UPC: \(numberSystem), \(manufacturer), \(product), \(check).")
case .qrCode(let productCode):
    print("QR code: \(productCode).")
}

Raw Values

Enums can also have raw values, which are prepopulated values for each case.

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

You can initialize an enum from a raw value using the init?(rawValue:) initializer.

let possiblePlanet = Planet(rawValue: 3)  // Output: Optional(Planet.earth)

Conclusion

Enumerations in Swift offer a robust way to group related values, enhancing code readability and safety. They can be simple lists of cases, or they can be more complex with associated values and raw values. Mastering enums will make your Swift code more organized and maintainable.