关联值符合CaseIterable，RawRepresentable的枚举 [英] Enum with associated value conforming to CaseIterable, RawRepresentable

问题描述

我正在尝试使具有关联值的枚举符合CaseIterable，RawRepresentable。使用rawValue初始化时，我可以为关联值使用一些默认值。

I'm trying to make enum with associated value conform to CaseIterable, RawRepresentable. I'm fine with some default values for associated values when initializing by rawValue.

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]
    }
}

有没有办法通过手动切换所有情况下，即没有这样的代码：

Is there any way to make it without switching manually by all the cases, i.e. without such code:

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

值得注意的是，非常相似的代码也很好用，例如

What's notable is that very similar code works just fine, for example

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"
}

推荐答案

我终于可以使用 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
    })!
}

不要介意展开力，在这里很安全。

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

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