Swift Codable多种类型

问题描述

我尝试解析返回json对象的api。我的问题是，某些键有时是字符串，有时是诸如以下示例中的键 Value之类的对象：

I try to parse an api returning a json object. My problem is that some keys are sometime a string, sometime an object like the key "Value" in the following example:

[
{
    "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：

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"
        }
    }

我必须设法确保我完全迷失了（是的，我是个快速入门的人），我找不到解决问题的方法。我了解我必须使用自定义init，但我不知道如何使用。

I have to admin that I am totally lost (yes, I am a beginner in swift) and I can't find a solution to my problem. I understand that I have to use a custom init, but I don't know how.

推荐答案

您可以尝试

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)
}

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