How to sort objects by its enum value? - swift

Question

I've got Workout class with Difficulty property
enum Difficulty: String {
case easy = "easy"
case moderate = "moderate"
case hard = "hard"
}
class Workout {
var name: String?
var difficulty: Difficulty?
.
.
.
}
I'd like to sort an array of workouts by the difficulty property. I know I can achieve that by assigning enum's raw value to Int value and compare these values as follows:
data.sort { $0.workout.difficulty!.rawValue < $1.workout.difficulty!.rawValue }
But I really want this enum to store string, since it's convenient to assign it to label text down the line without ugly switch-case hacks, and be comparable in some way.
How to achieve that?

Answer 1

Implement the Comparable protocol on your enum. It gives you a static func < (lhs: Difficulty, rhs: Difficulty) -> Bool method where you define the sort.
Here is a full sample using a property to simplify the ordering
enum Difficulty: String, Comparable {
case easy = "easy"
case moderate = "moderate"
case hard(String) = "hard"
private var sortOrder: Int {
switch self {
case .easy:
return 0
case .moderate:
return 1
case .hard(_):
return 2
}
}
static func ==(lhs: Difficulty, rhs: Difficulty) -> Bool {
return lhs.sortOrder == rhs.sortOrder
}
static func <(lhs: Difficulty, rhs: Difficulty) -> Bool {
return lhs.sortOrder < rhs.sortOrder
}
}
Making it possible to use
data.sort { $0.workout.difficulty! < $1.workout.difficulty! }

Answer 2

edit/update: Swift 5.1 or later
You can change your enumeration RawValue type to integer and use its rawValue to sort your Workouts. Btw you should use a structure instead of a class and similar to what was suggested by Igor you could make your struct comparable instead of the enumeration:
struct Workout {
let name: String
let difficulty: Difficulty
}
extension Workout {
enum Difficulty: Int { case easy, moderate, hard }
}
extension Workout: Comparable {
static func <(lhs: Workout, rhs: Workout) -> Bool { lhs.difficulty.rawValue < rhs.difficulty.rawValue }
}
let wk1 = Workout(name: "night", difficulty: .hard)
let wk2 = Workout(name: "morning", difficulty: .easy)
let wk3 = Workout(name: "afternoon", difficulty: .moderate)
let workouts = [wk1, wk2, wk3] // [{name "night", hard}, {name "morning", easy}, {name "afternoon", moderate}]
let sorted = workouts.sorted() // [{name "morning", easy}, {name "afternoon", moderate}, {name "night", hard}]