Enum in Swift

According to the Swift documentation enumeration is defined as “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”.

The easiest way to think about enums is as structured lists of related items. A few examples:

• Gender: Male, Female and Others
• Designation: Mr, Miss, Mrs and Master

How to create an enum?

1. It’s simple just follow up your enum name after the keyword enum just like we declare classes in Swift.
2. The body of enum can include a number of cases followed by a case keyword. Cases in enum are the different values that an enum has.

enum Gender {
    case male
    case female
    case other
}

Raw Values Of Enums

Enum cases can be populated with a static raw value. If we take the same example from above the code of our Gender enum will look like this:

enum Gender: String {
    case male = “Male”
    case female = “Female”
    case other = “Other”
}

Now the Gender enum cases contain their own raw value of datatype String. Raw values can be strings, characters, or any of the integer or floating-point number types.

How can the raw value of enum be used?

• Getting raw value of enum case

let gender = Gender.male
print(gender.rawValue)
//Output: Male

• Construct a value of enum

let gender = Gender(rawValue: “Male”)
print(gender)
//Output: Optional(Gender.male)

Enum initialized with initializer returns an optional enum value because enum cannot be initialized if provided with a raw value that cannot be represented by the enum.

The value of the enum case can be used in a switch like below:

switch gender {
case .male:
    print(“Your designation must be Mr or Master, right?”)
case .female:
    print(“Your designation must be Miss or Mrs, right?”)
case .other:
    print(“Dear respected client, what should I call you?”)
}

Associated Values In Enums

Enums with associated values let us associate extra data with an enum case.

For this we take the next example of Ice cream Flavors as ice cream can have different numbers of scoops on its cone.

In order to make an associated value for enum just set the Data Types to receive for each case like this:

enum Flavour {
    case strawberry(numOfScoops: Int)
    case vanilla(numOfScoops: Int)
    case chocolate(numOfScoops: Int)
}
let flavour = Flavour.chocolate(numOfScoops: 2)
print(flavour)
//Output: chocolate(2)

The associated value of the enum case can be used like the example below:

switch flavour {
case .strawberry(let numOfScoops):
    print(“\(numOfScoops) scoops of Strawberry ice cream please!”)
case .vanilla(let numOfScoops):
    print(“\(numOfScoops) scoops of Vanilla ice cream please!”)
case .chocolate(let numOfScoops):
    print(“\(numOfScoops) scoops of Chocolate ice cream please!”)
}

Bonus Tip

Enums can have its methods and properties which can be used on enum cases.

enum Day: String {
case sunday
case monday
case tuesday
case wednesday
case friday
case saturday
//property
var isWorkingDay: Bool {
    switch self {
        case .saturday,
        .sunday:
        return false
    default:
        return true
    }
}
func moodDescription() -> String {
    return self.isWorkingDay? “I am sadly busy right now!” : “I am free to travelling”
}
}
print(Day.sunday.moodDescription())
//Output: I am free to travelling
print(Day.sunday.isWorkingDay)
//Output: false

Further Read

Enumerations - The Swift Programming Language (Swift 5.2)