Question

我试图使具有关联值的枚举符合CaseIterable，RawRepresentable。当用rawValue初始化时，我对关联值的一些默认值很好。

enum GenresAssociated: CaseIterable, RawRepresentable, Equatable {
    case unknown(String)
    case blues(String)
    case classical(String)
    // Implementing CaseIterable
    typealias AllCases = [GenresAssociated]
    // Enums can have no storage, but the class they are in CAN. Note 'static' in declaration
    static var allCases: [GenresAssociated] = [.unknown(""), .blues(""), .classical("")]


    typealias RawValue = Int
    var rawValue: Int {

        // MARK: This causes a crash for unknown reason
        return GenresAssociated.allCases.firstIndex(where: {  if case self = $0 { return true } else { return false } } ) ?? 0
    }
    init?(rawValue: Int) {
        guard GenresAssociated.allCases.indices.contains(rawValue) else { return nil }
        self = GenresAssociated.allCases[rawValue]
    }
}

有没有办法在所有情况下都无需手动切换，即没有这样的代码：

    typealias RawValue = Int
    var rawValue: Int {
        switch self {
        case .unknown:
            return 0
        case .blues:
            return 1
        case .classical:
            return 2
        }
    }

例如，非常相似的代码可以正常工作

enum EnumWithValue {
    case one(NSString!), two(NSString!), three(NSString!)
}

let arrayOfEnumsWithValues: [EnumWithValue] = [.one(nil), .two(nil), .three("Hey")]

if let index = arrayOfEnumsWithValues.firstIndex(where: { if case .two = $0 { return true }; return false }) {
    print(".two found at index \(index)") //prints ".two found at index 1"
}

Answer 1

I got it finally to work with Mirror!

var rawValue: Int {
    let selfCaseName = Mirror(reflecting: self).children.first!.label!

    return GenresAssociated.allCases.firstIndex(where: { (genre) in
        let switchingCaseName = Mirror(reflecting: genre).children.first!.label!

        return switchingCaseName == selfCaseName
    })!
}

Don't mind the force unwrapping, it is safe here.

Answer 2

此参数适用于包含 rawValue 案例和具有关联值的案例的枚举：

var caseName: String { 
   let result = String(describing: self)
   let assocValName = Mirror(reflecting: self).children.first?.label ?? "failed"

   return !result.contains("(") ? result : assocValName
}

关联值符合CaseIterable，RawRepresentable的枚举

2 个答案: