如何使用嵌套JSON结构和未知密钥的Swift Codable

Question

我有一个嵌套的json结构。 我知道顶级键（对象），但每次获取可能存在也可能不存在。 对象中的每个键（以及嵌套在其中的键）都是未知的。 他们很有活力。

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

以下是我的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...依此类推。每个顶级对象也是可选的。

我尝试了很多东西，但这些东西看起来最有希望（它们都不起作用，所以）

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))

2.  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，但真的很重要：

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

很难说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解码为更有用的Swift对象。

最简单的方法是将其建模为您呈现的数据结构。 例如，看起来someNumbers是一个由String键入的可选字典，其Int值为： [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加可读性，可以引入一些类型的别名，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?
}

为了获得有用的东西，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，循环使用更有意义

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