如何使用带有嵌套 JSON 结构和未知键的 Swift Codable

Question

我有一个嵌套的 json 结构。我知道顶级键（对象），但每次提取可能存在也可能不存在。对象中的每个键（以及嵌套在这些对象中的键）都是未知的。它们是动态的。

我已经尝试了几个小时来使用 Codable 来代替 JSONSerialization。在我完全失去希望之前，我想看看是否有人对此有解决方案。

这是我的 JSON 的示例：

var jsonString =
"""
{
    "someNumbers": {
        "22": 6,
        "22626": 0
    },
    "someNestedAny": {
        "61": {
            "browser": 2
        },
        "8310": {
            "desktop": 2
        }
    },
    "someNestedArray": {
        "49": ["Chrome"],
        "50": ["Mac OS X"],
        "51": ["Mac desktop"],
        "52": ["browser"],
        "53": ["Chrome"]
    }
}
""" 

每个顶级对象中的键值对（someNumbers、someNestedAny 和 someNestedArray 是动态的。这些对象中的键/值也是动态的......等等。每个顶级对象也是可选的。

我尝试了很多东西，但这些都是看起来最有希望的（但它们都没有奏效）

1. 
   struct TopLevel: Decodable {
       var someNumbers: SomeNumbers?
       var someNestedAny: SomeNestedAny?
       var someNestedArray: SomeObjectFromNestedAny?
   }
   
   struct SomeNumbers: Decodable {
       var key: String
       var value: Int
   }
   
   struct SomeNestedAny: Decodable {
       var key: String
       var value: SomeObjectFromNestedAny
   }
   
   struct SomeObjectFromNestedAny: Decodable {
       var key: String
       var value: Int
   }
   
   struct SomeNestedArray: Decodable {
       var key: String
       var value: [String]
   }
   
   let data = jsonString.data(using: .utf8)!
   do {
       let result = try JSONDecoder().decode(TopLevel.self, from: data)
       print(result)
   } catch {
       print(error)
   }
   

输出：keyNotFound(CodingKeys(stringValue: "key", intValue: nil), Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "someNumbers", intValue: nil)], debugDescription: "No value associated with key CodingKeys(stringValue: \"key\", intValue: nil) (\"key\").", underlyingError: nil))

1. struct TopLevel: Decodable {
       var someNumbers: SomeNumbers?
       var someNestedAny: SomeNestedAny?
       var someNestedArray: SomeObjectFromNestedAny?
   }
   
   struct SomeNumbers: Decodable {
   
       public var numbersObject: [String: NumberKeys]
   
       public struct NumberKeys: Decodable {
           public let key: String
           public let value: Int
       }
   
       private struct NumberCodingKeys: CodingKey {
           var stringValue: String
   
           init?(stringValue: String) {
               self.stringValue = stringValue
           }
   
           var intValue: Int?
   
           init?(intValue: Int) {
               return nil
           }
       }
   
       public init(from decoder: Decoder) throws {
           let container = try decoder.container(keyedBy: NumberCodingKeys.self)
           self.numbersObject = [String: NumberKeys]()
           for key in container.allKeys {
               let value = try container.decode(NumberKeys.self, forKey: NumberCodingKeys(stringValue: key.stringValue)!)
               self.numbersObject[key.stringValue] = value
           }
   
       }
   }
   
   struct SomeNestedAny: Decodable {
       // was going to do the same thing as above - but it didn't work
       var key: String
       var value: SomeObjectFromNestedAny
   }
   
   struct SomeObjectFromNestedAny: Decodable {
       // was going to do the same thing as above - but it didn't work
       var key: String
       var value: Int
   }
   
   struct SomeNestedArray: Decodable {
       // was going to do the same thing as above - but it didn't work
       var key: String
       var value: [String]
   }
   
   let data = jsonString.data(using: .utf8)!
   do {
       let result = try JSONDecoder().decode(TopLevel.self, from: data)
       print(result)
   } catch {
       print(error)
   }
   

输出：typeMismatch(Swift.Dictionary<Swift.String, Any>, Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "someNumbers", intValue: nil), NumberCodingKeys(stringValue: "22626", intValue: nil)], debugDescription: "Expected to decode Dictionary<String, Any> but found a number instead.", underlyingError: nil))

这是我现在的工作，但真的很恶心：

let data = jsonString.data(using: .utf8)
let json = try JSONSerialization.jsonObject(with: data!) as! [String:Any]
if let numbers = json["someNumbers"] as? [String:Any] {
    for (key, value) in numbers {
        print("key: \(key), value: \(value)")
    }
}
if let anys = json["someNestedAny"] as? [String: Any] {
    //print("tkey: \(anys)")
    for (key, value) in anys {
        //print("tkey2: \(key), tvalue: \(value)")
        if let value = value as? [String: Any] {
            let anyData = try JSONSerialization.data(withJSONObject: value, options: .prettyPrinted)
            let anyJson = try JSONSerialization.jsonObject(with: anyData) as! [String: Any]
            for (key2, value2) in anyJson {
                print("key: \(key), object-key: \(key2), object-value: \(value2)")
            }
        }
    }
}
if let arrays = json["someNestedArray"] as? [String: Any] {
    for (key, value) in arrays {
        print("key: \(key), value: \(value)")
    }
}

提前致谢！

Answer 1

很难判断这是否能解决您的确切用例，因为我不确定数据的用途是什么，以及您预期如何使用它，但以下两种解决方案都能正确地将您的 JSON 解码为更多可用的 Swift 对象。

最简单的方法是将其完全建模为您提供的数据结构。例如，看起来someNumbers 是由String 键入的可选字典，Int 值：[String: Int]?。

struct TopLevel: Decodable {
  var someNumbers: [String: Int]?
  var someNestedAny: [String: [String: Int]]?
  var someNestedArray: [String: [String]]?
}

为了在传递对象时更具可读性，您可以添加一些类型别名，然后它就变成了

typealias SomeNumbers = [String: Int]
typealias SomeNestedAny = [String: [String: Int]]
typealias SomeNestedArray = [String: [String]]

struct TopLevel: Decodable {
  var someNumbers: SomeNumbers?
  var someNestedAny: SomeNestedAny?
  var someNestedArray: SomeNestedArray?
}

为了得到有用的东西，你需要调用类似的东西

topLevel.someNumbers?["22"]                 // 6
topLevel.someNestedAny?["8310"]             // ["desktop": 2]
topLevel.someNestedAny?["8310"]?["desktop"] // 2
topLevel.someNestedArray?["52"]             // ["browser"]
topLevel.someNestedArray?["52"]?[0]         // "browser"

或者根据您的需要，循环访问可能更有意义

topLevel.someNestedAny?
  .forEach { item in
    print("|- \(item.key)")
    item.value.forEach { any in
      print("|  |- \(any.key)")
      print("|  |  |- \(any.value)")
    }
}

// |- 61
// |  |- browser
// |  |  |- 2
// |- 8310
// |  |- desktop
// |  |  |- 2