Question

我已经Workout有Difficulty属性

的课程

enum Difficulty: String {
  case easy = "easy"
  case moderate = "moderate"
  case hard = "hard"
}

class Workout {
  var name: String?
  var difficulty: Difficulty?
  .
  .
  .
}

我想通过难度属性对一系列训练进行排序。我知道我可以通过将枚举的原始值分配给Int值来实现这一点，并按如下方式比较这些值：

data.sort { $0.workout.difficulty!.rawValue < $1.workout.difficulty!.rawValue }

但是我真的希望这个枚举能够存储字符串，因为它可以方便地将它分配给标签文本而不会出现丑陋的开关案例，并且在某些方面具有可比性。

如何实现？

Answer 1

在Comparable上实施enum协议。它为您提供了static func < (lhs: Difficulty, rhs: Difficulty) -> Bool方法，您可以在其中定义排序。

以下是使用属性简化排序的完整示例

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
    }
}

可以使用

data.sort { $0.workout.difficulty! < $1.workout.difficulty! }

Answer 2

您可以使用枚举hashValue对锻炼进行排序。您应该使用结构而不是类，并且类似于Igor建议的结构，您可以使结构具有可比性，而不是枚举：

struct Workout: Comparable {
    let name: String
    let difficulty: Difficulty
    enum Difficulty: String {
        case easy, moderate, hard
    }
    static func ==(lhs: Workout, rhs: Workout) -> Bool {
        return lhs.difficulty.hashValue == rhs.difficulty.hashValue
    }
    static func <(lhs: Workout, rhs: Workout) -> Bool {
        return lhs.difficulty.hashValue < rhs.difficulty.hashValue
    }
}

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}]

如何按枚举值对对象进行排序？

2 个答案: