快速解码JSON，其中JSON具有相同字段的两种可能类型

问题描述

我正在使用Alamofire和Codable处理此JSON：

[
    {
        "pID": "37229890-dcd8-36c4-bb63-e7b174aafeb7","type": "FIRST","content": {
            "id": "ff64","ret": {
                "name": "A","logoUrl": "hpng"
            },"amo": {
                "value": 120.00,"currency": "EUR"
            },"s": {
                "value": 1.20,"datetime": "","p": [
                {
                    "ti": "","pr": {
                        "value": 120.00,"currency": "EUR"
                    },"pic": "string"
                }
            ]
        }
    },{
        "pID": "37229890-dcd8-36c4-bb63-e7b174aafeb7","type": "RATE","content": "Rate this app"
    }
]

如您所见，“ content”类型的te值可以是简单的String或Struct。

我已经尝试过使用自定义解码器并具有顶级结构，但无法解决此问题。

解决此问题的最佳方法是什么？

解决方法

这是您所期望的吗？

let json = """
[
    {
        "type": "type1","content": {
            "id": "ff64","title": "a title"
        }
    },{
        "type": "type2","content": "Rate this app"
    }
]
"""

struct Type1: Decodable {
  let id: String
  let title: String
}

typealias Type2 = String

enum Content: Decodable {
  case type1(Type1)
  case type2(Type2)

  enum ContentType: String,Decodable {
    case type1
    case type2
  }

  enum Keys: String,CodingKey {
    case type
    case content
  }

  init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: Keys.self)
    let type = try container.decode(ContentType.self,forKey: .type)

    switch type {
    case .type1:
      let content = try container.decode(Type1.self,forKey: .content)
      self = .type1(content)
    case .type2:
      let content = try container.decode(Type2.self,forKey: .content)
      self = .type2(content)
    }
  }
}

let result = try JSONDecoder().decode([Content].self,from: json.data(using: .utf8)!)

,

您可以应用AnyCodable自定义解码器方法，该方法可以解码所需的类型，例如：

struct AnyCodable : Codable {
    let value: Any
    
    func encode(to encoder: Encoder) throws {
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        
        if let str = try? container.decode(String.self) {
            value = str
        } else if let content = try? container.decode(Content.self) {
            value = content
        } else {
            throw DecodingError.dataCorruptedError(in: container,debugDescription: "Value cannot be decoded!")
        }
    }
}

struct Content : Codable {
    let id: String
}

struct Item : Codable {
    let content: AnyCodable
}

使用方法：

do {
    let items = try JSONDecoder().decode([Item].self,from: json.data(using: .utf8)!);
    for item in items {
        if let content = item.content.value as? String {
            print(content)
        }
        else if let content = item.content.value as? Content {
            print(content.id)
        }
    }
}
catch {
    print(error)
}