如何使用 Swift 的 Codable 编码成字典？

Question

我有一个实现 Swift 4 的 Codable 的结构。是否有一种简单的内置方法将该结构编码到字典中？

let struct = Foo(a: 1, b: 2)
let dict = something(struct)
// now dict is ["a": 1, "b": 2]

Answer 1

我不确定这是否是最好的方法，但你绝对可以这样做：

struct Foo: Codable {
    var a: Int
    var b: Int

    init(a: Int, b: Int) {
        self.a = a
        self.b = b
    }
}

let foo = Foo(a: 1, b: 2)
let dict = try JSONDecoder().decode([String: Int].self, from: JSONEncoder().encode(foo))
print(dict)

Answer 2

我写了一个快速的 gist 来处理这个问题（不使用 Codable 协议）。请注意，它不会对任何值进行类型检查，也不会递归地处理可编码的值。

class DictionaryEncoder {
    var result: [String: Any]

    init() {
        result = [:]
    }

    func encode(_ encodable: DictionaryEncodable) -> [String: Any] {
        encodable.encode(self)
        return result
    }

    func encode<T, K>(_ value: T, key: K) where K: RawRepresentable, K.RawValue == String {
        result[key.rawValue] = value
    }
}

protocol DictionaryEncodable {
    func encode(_ encoder: DictionaryEncoder)
}

Answer 3

想想看，这个问题在一般情况下没有答案，因为 Encodable 实例可能是无法序列化到字典中的东西，例如数组：

let payload = [1, 2, 3]
let encoded = try JSONEncoder().encode(payload) // "[1,2,3]"

除此之外，我写了something similar as a framework。

Answer 4

如果您不介意稍微移动一下数据，您可以使用类似这样的方法：

extension Encodable {
  func asDictionary() throws -> [String: Any] {
    let data = try JSONEncoder().encode(self)
    guard let dictionary = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String: Any] else {
      throw NSError()
    }
    return dictionary
  }
}

或可选变体

extension Encodable {
  var dictionary: [String: Any]? {
    guard let data = try? JSONEncoder().encode(self) else { return nil }
    return (try? JSONSerialization.jsonObject(with: data, options: .allowFragments)).flatMap { [=11=] as? [String: Any] }
  }
}

假设Foo符合Codable或者真的Encodable那么你可以这样做。

let struct = Foo(a: 1, b: 2)
let dict = try struct.asDictionary()
let optionalDict = struct.dictionary

如果你想走另一条路(init(any))，看看这个Init an object conforming to Codable with a dictionary/array

Answer 5

let dict = try JSONSerialization.jsonObject(with: try JSONEncoder().encode(struct), options: []) as? [String: Any]

Answer 6

我已经创建了一个名为 CodableFirebase 的库，它的最初目的是将它与 Firebase 数据库一起使用，但它实际上满足了您的需要：它创建了一个字典或任何其他类型，就像 [=11] =] 但你不需要像在其他答案中那样在这里进行双重转换。所以它看起来像：

import CodableFirebase

let model = Foo(a: 1, b: 2)
let dict = try! FirebaseEncoder().encode(model)

Answer 7

我绝对认为能够使用 Codable 来编码 to/from 字典是有一定价值的，而不是打算打 JSON/Plists/whatever。有很多 API 只是给你一个字典，或者期待一个字典，能够轻松地将它们与 Swift 结构或对象互换，而不必编写无休止的样板代码是很好的。

我一直在研究一些基于 Foundation JSONEncoder.swift 源代码的代码（它实际上在内部实现了字典 encoding/decoding，但不导出它）。

代码可以在这里找到：https://github.com/elegantchaos/DictionaryCoding

它仍然很粗糙，但我对其进行了一些扩展，例如，它可以在解码时使用默认值填充缺失值。

Answer 8

我修改了PropertyListEncoder from the Swift project into a DictionaryEncoder, simply by removing the final serialisation from dictionary into binary format. You can do the same yourself, or you can take my code from here

可以这样使用：

do {
    let employeeDictionary: [String: Any] = try DictionaryEncoder().encode(employee)
} catch let error {
    // handle error
}

Answer 9

在 Codable 中没有直接的方法可以做到这一点。您需要为您的结构实施 Encodable/Decodable 协议。对于您的示例，您可能需要编写如下

typealias EventDict = [String:Int]

struct Favorite {
    var all:EventDict
    init(all: EventDict = [:]) {
        self.all = all
    }
}

extension Favorite: Encodable {
    struct FavoriteKey: CodingKey {
        var stringValue: String
        init?(stringValue: String) {
            self.stringValue = stringValue
        }
        var intValue: Int? { return nil }
        init?(intValue: Int) { return nil }
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: FavoriteKey.self)

        for eventId in all {
            let nameKey = FavoriteKey(stringValue: eventId.key)!
            try container.encode(eventId.value, forKey: nameKey)
        }
    }
}

extension Favorite: Decodable {

    public init(from decoder: Decoder) throws {
        var events = EventDict()
        let container = try decoder.container(keyedBy: FavoriteKey.self)
        for key in container.allKeys {
            let fav = try container.decode(Int.self, forKey: key)
            events[key.stringValue] = fav
        }
        self.init(all: events)
    }
}

Answer 10

在某些项目中，我使用了 swift 反射。但是要小心，嵌套的可编码对象也没有映射到那里。

let dict = Dictionary(uniqueKeysWithValues: Mirror(reflecting: foo).children.map{ ([=10=].label!, [=10=].value) })

Answer 11

没有内置的方法可以做到这一点。作为如果您没有性能问题，那么您可以接受 JSONEncoder + JSONSerialization 实施。

但我宁愿采用标准库的方式来提供 encoder/decoder 对象。

class DictionaryEncoder {
    private let jsonEncoder = JSONEncoder()

    /// Encodes given Encodable value into an array or dictionary
    func encode<T>(_ value: T) throws -> Any where T: Encodable {
        let jsonData = try jsonEncoder.encode(value)
        return try JSONSerialization.jsonObject(with: jsonData, options: .allowFragments)
    }
}

class DictionaryDecoder {
    private let jsonDecoder = JSONDecoder()

    /// Decodes given Decodable type from given array or dictionary
    func decode<T>(_ type: T.Type, from json: Any) throws -> T where T: Decodable {
        let jsonData = try JSONSerialization.data(withJSONObject: json, options: [])
        return try jsonDecoder.decode(type, from: jsonData)
    }
}

您可以尝试使用以下代码：

struct Computer: Codable {
    var owner: String?
    var cpuCores: Int
    var ram: Double
}

let computer = Computer(owner: "5keeve", cpuCores: 8, ram: 4)
let dictionary = try! DictionaryEncoder().encode(computer)
let decodedComputer = try! DictionaryDecoder().decode(Computer.self, from: dictionary)

我在这里强制尝试使示例更短。在生产代码中，您应该适当地处理错误。

Answer 12

这里是 DictionaryEncoder / DictionaryDecoder 的简单实现，它包装了 JSONEncoder、JSONDecoder 和 JSONSerialization，还处理编码/解码策略……

class DictionaryEncoder {

    private let encoder = JSONEncoder()

    var dateEncodingStrategy: JSONEncoder.DateEncodingStrategy {
        set { encoder.dateEncodingStrategy = newValue }
        get { return encoder.dateEncodingStrategy }
    }

    var dataEncodingStrategy: JSONEncoder.DataEncodingStrategy {
        set { encoder.dataEncodingStrategy = newValue }
        get { return encoder.dataEncodingStrategy }
    }

    var nonConformingFloatEncodingStrategy: JSONEncoder.NonConformingFloatEncodingStrategy {
        set { encoder.nonConformingFloatEncodingStrategy = newValue }
        get { return encoder.nonConformingFloatEncodingStrategy }
    }

    var keyEncodingStrategy: JSONEncoder.KeyEncodingStrategy {
        set { encoder.keyEncodingStrategy = newValue }
        get { return encoder.keyEncodingStrategy }
    }

    func encode<T>(_ value: T) throws -> [String: Any] where T : Encodable {
        let data = try encoder.encode(value)
        return try JSONSerialization.jsonObject(with: data, options: .allowFragments) as! [String: Any]
    }
}

class DictionaryDecoder {

    private let decoder = JSONDecoder()

    var dateDecodingStrategy: JSONDecoder.DateDecodingStrategy {
        set { decoder.dateDecodingStrategy = newValue }
        get { return decoder.dateDecodingStrategy }
    }

    var dataDecodingStrategy: JSONDecoder.DataDecodingStrategy {
        set { decoder.dataDecodingStrategy = newValue }
        get { return decoder.dataDecodingStrategy }
    }

    var nonConformingFloatDecodingStrategy: JSONDecoder.NonConformingFloatDecodingStrategy {
        set { decoder.nonConformingFloatDecodingStrategy = newValue }
        get { return decoder.nonConformingFloatDecodingStrategy }
    }

    var keyDecodingStrategy: JSONDecoder.KeyDecodingStrategy {
        set { decoder.keyDecodingStrategy = newValue }
        get { return decoder.keyDecodingStrategy }
    }

    func decode<T>(_ type: T.Type, from dictionary: [String: Any]) throws -> T where T : Decodable {
        let data = try JSONSerialization.data(withJSONObject: dictionary, options: [])
        return try decoder.decode(type, from: data)
    }
}

用法类似于JSONEncoder / JSONDecoder…

let dictionary = try DictionaryEncoder().encode(object)

和

let object = try DictionaryDecoder().decode(Object.self, from: dictionary)

为方便起见，我将所有这些都放在了一个存储库中……https://github.com/ashleymills/SwiftDictionaryCoding

Answer 13

我在这里做了一个podhttps://github.com/levantAJ/AnyCodable方便解码和编码[String: Any]和[Any]

pod 'DynamicCodable', '1.0'

并且您能够解码和编码 [String: Any] 和 [Any]

import DynamicCodable

struct YourObject: Codable {
    var dict: [String: Any]
    var array: [Any]
    var optionalDict: [String: Any]?
    var optionalArray: [Any]?

    enum CodingKeys: String, CodingKey {
        case dict
        case array
        case optionalDict
        case optionalArray
    }

    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        dict = try values.decode([String: Any].self, forKey: .dict)
        array = try values.decode([Any].self, forKey: .array)
        optionalDict = try values.decodeIfPresent([String: Any].self, forKey: .optionalDict)
        optionalArray = try values.decodeIfPresent([Any].self, forKey: .optionalArray)
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(dict, forKey: .dict)
        try container.encode(array, forKey: .array)
        try container.encodeIfPresent(optionalDict, forKey: .optionalDict)
        try container.encodeIfPresent(optionalArray, forKey: .optionalArray)
    }
}

Answer 14

这是一个基于协议的解决方案：

protocol DictionaryEncodable {
    func encode() throws -> Any
}

extension DictionaryEncodable where Self: Encodable {
    func encode() throws -> Any {
        let jsonData = try JSONEncoder().encode(self)
        return try JSONSerialization.jsonObject(with: jsonData, options: .allowFragments)
    }
}

protocol DictionaryDecodable {
    static func decode(_ dictionary: Any) throws -> Self
}

extension DictionaryDecodable where Self: Decodable {
    static func decode(_ dictionary: Any) throws -> Self {
        let jsonData = try JSONSerialization.data(withJSONObject: dictionary, options: [])
        return try JSONDecoder().decode(Self.self, from: jsonData)
    }
}

typealias DictionaryCodable = DictionaryEncodable & DictionaryDecodable

下面是使用方法：

class AClass: Codable, DictionaryCodable {
    var name: String
    var age: Int
    
    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }
}

struct AStruct: Codable, DictionaryEncodable, DictionaryDecodable {
    
    var name: String
    var age: Int
}

let aClass = AClass(name: "Max", age: 24)

if let dict = try? aClass.encode(), let theClass = try? AClass.decode(dict) {
    print("Encoded dictionary: \n\(dict)\n\ndata from decoded dictionary: \"name: \(theClass.name), age: \(theClass.age)\"")
}

let aStruct = AStruct(name: "George", age: 30)

if let dict = try? aStruct.encode(), let theStruct = try? AStruct.decode(dict) {
    print("Encoded dictionary: \n\(dict)\n\ndata from decoded dictionary: \"name: \(theStruct.name), age: \(theStruct.age)\"")
}

Answer 15

这里是字典 -> 对象。 Swift5.

extension Dictionary where Key == String, Value: Any {

    func object<T: Decodable>() -> T? {
        if let data = try? JSONSerialization.data(withJSONObject: self, options: []) {
            return try? JSONDecoder().decode(T.self, from: data)
        } else {
            return nil
        }
    }
}

Answer 16

经过研究，我们发现在继承自Codable & Decodable的class中使用关键字Any会报错。因此，如果您想使用字典 user 来处理来自服务器的数据类型。例如，服务器正在发送 [String : Int] 类型的字典，然后使用 [String : Int] 如果你想尝试 [String : Any] 它将不起作用。

如何使用 Swift 的 Codable 编码成字典？

How can I use Swift’s Codable to encode into a dictionary?

swift

swift4

codable