Swift 按枚舉聲明的順序對枚舉數組進行排序

Question

如何對要按聲明順序排序的枚舉數組進行排序？

enum EducationOptions: String {
    case gcse = "GCSE"
    case aLevel = "A Level"
    case bachelors = "Bachelors"
    case masters = "Masters"
    case doctorate = "Doctorate"
    case other = "Other"
}

var arrayOfEducationOptions: [EducationOptions] = [.masters, .gcse, .aLevel]

我想按照枚舉中聲明的順序對 arrayOfEducationOptions 進行排序以獲取 [.gcse, .aLevel, .masters]

Answer 1

使其符合CaseIterable協議並使用靜態allCases屬性：

enum EducationOptions: String, CaseIterable {
    case gcse = "GCSE"
    case aLevel = "A Level"
    case bachelors = "Bachelors"
    case masters = "Masters"
    case doctorate = "Doctorate"
    case other = "Other"
}

let arrayOfEducationOptions = EducationOptions.allCases

Answer 2

看起來 Vadim 的想法是正確的，但是如果您想對 EducationOptions 的任意列表進行排序，您可以使用如下代碼：

enum EducationOptions: String, CaseIterable {
    case gcse = "GCSE"
    case aLevel = "A Level"
    case bachelors = "Bachelors"
    case masters = "Masters"
    case doctorate = "Doctorate"
    case other = "Other"
}

let allCases = EducationOptions.allCases

var arrayOfEducationOptions: [EducationOptions] = [.masters, .gcse, .aLevel]
    .sorted {allCases.firstIndex(of: $0)! <  allCases.firstIndex(of: $1)! }

arrayOfEducationOptions.forEach { print($0) }

請注意，該代碼是一個幼稚的實現，並且隨着案例數量的增加，擴展性會很差。 （它至少具有O(n²)時間性能，甚至可能更差（ O(n²•log n) ）。對於較大的枚舉，您需要重寫它以創建一個結構數組，其中包含來自示例數組的索引枚舉，然后排序。

Answer 3

向枚舉添加可比較的協議？

enum EducationOptions: String {
   case gcse = "GCSE"
   case aLevel = "A Level"
   case bachelors = "Bachelors"
   case masters = "Masters"
   case doctorate = "Doctorate"
   case other = "Other"

   var order: Int {
      switch self {
      case .gcse: return 1
      case .aLevel: return 2
      case .bachelors: return 3
      case .masters: return 4
      case .doctorate: return 5
      case .other: return 6
   }
}

extention EquctionOptions: Comparable { 


   static func < (lhs: EducationOptions, rhs: EducationOptions) -> Bool {
      lhs.order < rhs.order
   }
}

然后你可以對數組進行排序。

let array = [.masters, .gcse, .aLevel]
let sorted = array.sorted(by: { $0 < $1 })

可能有更好的方法來設置數組中的順序值，同時也具有字符串原始值，但不是我的頭頂