如何使用Swift枚举实现默认关联值？ [英] How should I implement Default Associated Values with Swift Enums?

问题描述

我有一个API给我可用的过滤器，它是不太可能，API可能会添加额外的过滤器类型。因此，如果API发送一个未知的过滤器类型，我想保留与枚举相关的信息。

以下是我对此的不同想法。

我的前两个尝试没有编译。我的第三个尝试只是觉得有点笨重。

有没有人有更好的方式这样做？你认为我不应该使用这个问题的枚举？

  typealias APIFilterIdentifier = String 
 
 / *不编译* / 
枚举EnumTestAssociatedValeu：APIFilterIdentifier {
 case Unknown（APIFilterIdentifier）
 case Everyone =everyone
 case Team =myteam
 
 
 / *不编译* / 
枚举EnumTestDefaultAssociatedValues：APIFilterIdentifier {
 case Unknown（APIFilterIdentifier）
 case Everyone（APIFilterIdentifier =everyone）
 case Team（APIFilterIdentifier =myteam）
} 
 
 / *编译但是有更好的方法吗？ * / 
枚举EnumTestWithCustomInit {
 
 case Unknown（APIFilterIdentifier）
 case Everyone 
 case Team 
 
 init（filterIdentifier：APIFilterIdentifier）{
让大家：APIFilterIdentifier = EnumTestWithCustomInit.everyoneFilterIdentifier 
让团队：APIFilterIdentifier = EnumTestWithCustomInit.teamFilterIdentifier 
 
 switch filterIdentifier {
 case everyone：
 self = .Everyone 
案例小组：
 self = .Team 
默认值：
 self = .Unknown（filterIdentifier）
} 
} 
 
 func asIdentifer（） - > APIFilterIdentifier {
 switch self {
 case .Everyone：
 return EnumTestWithCustomInit.everyoneFilterIdentifier 
 case .Team：
 return EnumTestWithCustomInit.teamFilterIdentifier 
 case .Unknown（let filterIdentifier）
 return filterIdentifier 
} 
} 
 
 private static var everyoneFilterIdentifier：APIFilterIdentifier {
 returneveryone
} 
 
 private static var teamFilterIdentifier：APIFilterIdentifier {
 returnmyteam
} 
} 
  

解决方案

我知道这有点老了，但这是否符合您的要求？

  typealias FilterIdentifier = String 
 
枚举DefaultAPIFilters：FilterIdentifier {
 case Everyone =everyone
 case Team =team
} 
 
枚举APIFilters {
 case默认（DefaultAPIFilters） 
 case自定义（FilterIdentifier）
} 
 
让everyoneFilter = APIFilters.Default（.Everyone）
让teamFilter = APIFilters.Default（.Team）
让clownFilter = APIFilters.Custom（clowns_only）
  

Swift question is there a way of having an enum type with one case that can have an associated value.

I have an API that gives me available filters, it's unlikely but possible that the API will add additional filter types. So if the API sends an unknown filter type I want to keep that information associated with the enum.

Below are the different ideas I had about doing this.

My first two tries didn't compile. My third try just feels a bit clunky.

Does anyone have a better way of doing this? Do you think I just shouldn't use an enum for this problem?

typealias APIFilterIdentifier = String

/* Does Not Compile */
enum EnumTestAssociatedValeu: APIFilterIdentifier {
    case Unknown(APIFilterIdentifier)
    case Everyone = "everyone"
    case Team = "myteam"
}

/* Does not compile */
enum EnumTestDefaultAssociatedValues: APIFilterIdentifier {
    case Unknown(APIFilterIdentifier)
    case Everyone(APIFilterIdentifier = "everyone")
    case Team(APIFilterIdentifier = "myteam")
}

/* Compiles but is there a better way? */
enum EnumTestWithCustomInit {

    case Unknown(APIFilterIdentifier)
    case Everyone
    case Team

    init(filterIdentifier: APIFilterIdentifier) {
        let everyone: APIFilterIdentifier = EnumTestWithCustomInit.everyoneFilterIdentifier
        let team: APIFilterIdentifier = EnumTestWithCustomInit.teamFilterIdentifier

        switch filterIdentifier {
        case everyone:
            self = .Everyone
        case team:
            self = .Team
        default:
            self = .Unknown(filterIdentifier)
        }
    }

    func asIdentifer() -> APIFilterIdentifier {
        switch self {
        case .Everyone:
            return EnumTestWithCustomInit.everyoneFilterIdentifier
        case .Team:
            return EnumTestWithCustomInit.teamFilterIdentifier
        case .Unknown(let filterIdentifier):
            return filterIdentifier
        }
    }

    private static var everyoneFilterIdentifier: APIFilterIdentifier {
        return "everyone"
    }

    private static var teamFilterIdentifier: APIFilterIdentifier {
        return "myteam"
    }
}

解决方案

I know this is a bit old, but would this work for what you want?

typealias FilterIdentifier = String

enum DefaultAPIFilters: FilterIdentifier {
    case Everyone = "everyone"
    case Team = "team"
}

enum APIFilters {
    case Default(DefaultAPIFilters)
    case Custom(FilterIdentifier)
}

let everyoneFilter = APIFilters.Default(.Everyone)
let teamFilter = APIFilters.Default(.Team)
let clownFilter = APIFilters.Custom("clowns_only")

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