Enums

An enum (enumeration) defines a type with a fixed set of possible values, called cases. Use one whenever a value must be one of a known list of options.

Syntax and example

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

var heading = Direction.north
heading = .east

switch heading {
case .north: print("Up")
case .south: print("Down")
case .east: print("Right")
case .west: print("Left")
}
print(heading)

Expected output

Right
east

• Once Swift knows the type, you can write just .east.
• The switch needs no default because it covers every case. If you later add case up, the compiler flags every switch that doesn't handle it — a huge help when code changes.

Raw values

Cases can carry a fixed raw value of a simple type:

enum Planet: Int {
    case mercury = 1, venus, earth, mars
}

enum Status: String {
    case active, suspended = "on_hold"
}

print(Planet.earth.rawValue)
print(Status.suspended.rawValue)
print(Planet(rawValue: 4) == .mars)
print(Status(rawValue: "deleted") == nil)

3
on_hold
true
true

Integer raw values count up automatically; string raw values default to the case name. Planet(rawValue:) is a failable initializer — ideal for turning stored or received data back into an enum.

Methods, computed properties, and CaseIterable

enum Size: CaseIterable {
    case small, medium, large

    var price: Double {
        switch self {
        case .small: 2.5
        case .medium: 3.0
        case .large: 3.5
        }
    }
}

for size in Size.allCases {
    print("\(size): $\(size.price)")
}

small: $2.5
medium: $3.0
large: $3.5

CaseIterable gives you allCases — every case, in order.

Common mistakes

• Using strings like "small" for a fixed set of options. A typo in a string is a silent bug; a typo in an enum case is a compile error.
• Adding a default to a switch over your own enum. It hides the compile error you'd otherwise get when a new case is added.