Swift enumerations

Enumerations or Enums are a way to define your own kind of value, you can define the data type and then the values that it holds.

Copyenum Roles {
    case admin
    case user
    case guest
}

Switch statement

Enums can be used to match with switch statements as we can sew below.

Copyenum Roles {
    case admin
    case user
    case guest
}

func logUserRole(role roles: Roles) {
    switch roles {
        case admin:
            print("This is an admin user.")
        case user:
            print("This is a regular user.")
        default:
            print("This is a guest user.")
    }
}

logUserRole(role: .guest)

If its not appropriate to provide a case for all enums Swift allows us to provide a "default" case.

Raw values

Raw values allows us to attach a value to our enum cases. These cases can be a string, integer, or any floating-point, just make sure the values are of type we set.

Copyenum Roles: String {
    case admin = "Administrator user"
    case user = "Regular user"
    case guest = "Guest user"
}

let role: Roles = .admin
print(role.rawValue)

Caseiterable

Using caseiterable makes our enum confirm to the CaseIterable protocol which gives us access to specific properties like "allCases" & "AllCases". With caseiterable our enum gets put into a collection which we can then use.

Copyenum Roles: CaseIterable {
    case admin, user, guest
}

print(Roles.allCases.count)

In the example above we have used "allCases" property to print out the number of cases in the enum collection.

Copyenum Roles: String, CaseIterable {
    case admin = "Administrator user"
    case user = "Regular user"
    case guest = "Guest user"
}

print(Roles.allCases.count)
for role in Roles.allCases {
    print(role.rawValue)
}

In the example above we have used "allCases" property to print out the eawValue of each case in the enum collection.

Pro tip: Enums can have methods, subscripts, and computed properties but not the stored properties.

Associated values

Associated values are used for storing specific values in our enum cases. The best part is we can store the values of any type and those value types can be different in each case.

Copyenum MobileDevices {
    case ios
    case android
}

enum Components {
    case backend(version: String)
    case frontend(version: String)
    case mobile(type: MobileDevices, version: String)
}

let component: Components = .mobile(type: .ios, version: "1.0.0")
print(component)

Conclusion

Enumerations are useful when it comes to deal with states, and we can quickly respond to different use cases by using switch, and thanks to type-safety in Swift, we can safely wrangle any group of related values that come our way.