Swift 可编码多种类型

Question

我尝试解析一个 api 并返回一个 json 对象。我的问题是有些键有时是一个字符串，有时是一个对象，例如以下示例中的键 "Value"：

[
{
    "Description": null,
    "Group": "Beskrivning av enheten",
    "GroupDescription": null,
    "Id": "Description",
    "Name": "Mer om enheten",
    "Value": "Det finns möjlighet till parkering på gatorna runt om, men det är kantstenar och ganska branta backar för att komma upp till lekplatsen.\r\n\r\nUtanför själva lekplatsen finns en gungställning med en plan omväg in. Alla lekredskap står i sandytor, det finns många kanter. Runt hela lekplatsen går ett staket med öppningar i olika riktningar."
},
{
    "Description": null,
    "Group": "Bilder och film",
    "GroupDescription": null,
    "Id": "Image",
    "Name": "Huvudbild",
    "Value": {
        "__type": "FileInfo",
        "Id": "8871b3b1-14f4-4054-8728-636d9da21ace",
        "Name": "ullerudsbacken.jpg"
    }
}
]

我的结构如下所示：

struct ServiceUnit: Codable {
        let description: String?
        let group: String?
        let groupDescription: String?
        let id: String
        let name: String
        var value: String?
        struct ServiceUnitTypeInfo: Codable {
            let id: String
            let singularName: String?
            enum CodingKeys: String, CodingKey {
                case id = "Id"
                case singularName = "SingularName"
            }
        }
        let serviceUnitTypeInfo: ServiceUnitTypeInfo?
        let values: [String]?
        enum CodingKeys: String, CodingKey {
            case description = "Description"
            case group = "Group"
            case groupDescription = "GroupDescription"
            case id = "Id"
            case name = "Name"
            case value = "Value"
            case serviceUnitTypeInfo = "ServiceUnitTypeInfo"
            case values = "Values"
            case image = "Image"
        }
    }

我不得不承认我完全迷路了（是的，我是 swift 的初学者）而且我找不到解决我的问题的方法。我知道我必须使用自定义初始化，但我不知道如何。

Answer 1

你可以试试

struct Root: Codable {
    let description,id: String
    let group,groupDescription: String?
    let name: String
    let value: MyValue

    enum CodingKeys: String, CodingKey {
        case description = "Description"
        case group = "Group"
        case groupDescription = "GroupDescription"
        case id = "Id"
        case name = "Name"
        case value = "Value"
    }
}

enum MyValue: Codable {
    case string(String)
    case innerItem(InnerItem)

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        if let x = try? container.decode(String.self) {
            self = .string(x)
            return
        }
        if let x = try? container.decode(InnerItem.self) {
            self = .innerItem(x)
            return
        }
        throw DecodingError.typeMismatch(MyValue.self, DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Wrong type for MyValue"))
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        switch self {
        case .string(let x):
            try container.encode(x)
        case .innerItem(let x):
            try container.encode(x)
        }
    }
}

struct InnerItem: Codable {
    let type, id, name: String

    enum CodingKeys: String, CodingKey {
        case type = "__type"
        case id = "Id"
        case name = "Name"
    }
}

do {
  let result = try JSONDecoder().decode([Root].self,from:data)
  print(result)
}
catch {
  print(error)
}

Answer 2

基于@Sh_Khan 的回答并在评论中回答@Nikhi 的问题（您如何访问这些值）我喜欢将其添加到枚举声明中：

var innerItemValue: InnerItem? {
    switch self {
    case .innerItem(let ii):
        return ii
    default:
        return nil
    }
}

var stringValue: String? {
    switch self {
    case .string(let s):
        return s
    default:
        return nil
    }
}

Swift 可编码多种类型

Swift Codable multiple types

swift

codable

decodable