Des problèmes pour décoder JSON avec Codable ?

Question

Avec Swift 3 JSONSerialization Si une partie de votre modèle de données est complètement dynamique, vous pouvez toujours laisser les données désérialisées à l'endroit où elles se trouvent. Any et laisser le consommateur s'en occuper.

Avec le système Swift 4 Codable J'aimerais le faire :

struct Foo : Codable {
    let bar: Any;
}

Mais je reçois

JSONPlayground.playground:4:9: note: cannot automatically synthesize 'Decodable' because 'Any' does not conform to 'Decodable'
    let bar: Any;
        ^

Cela ne serait pas la fin du monde si je pouvais mettre en œuvre mon propre système. Decodable mais cela nécessiterait la mise en place d'un Decoder pour permettre le décodage vers Any ce qui, à ma connaissance, n'est pas le cas. Par exemple :

extension Foo {
    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        let result = try container.decode(AnyClass.self)
    }
}

donne

error: JSONPlayground.playground:4:36: error: cannot invoke 'decode' with an argument list of type '(AnyClass.Protocol)'
        let result = try container.decode(AnyClass.self)
                                   ^

Existe-t-il une solution à ce problème ?

Answer 1

J'ai fini par devoir implémenter ma propre classe pour encoder/décoder Any valeurs. Ce n'est pas très joli, mais cela semble fonctionner :

class JSONAny: Codable {
    public let value: Any

    static func decodingError(forCodingPath codingPath: [CodingKey]) -> DecodingError {
        let context = DecodingError.Context(codingPath: codingPath, debugDescription: "Cannot decode JSONAny")
        return DecodingError.typeMismatch(JSONAny.self, context)
    }

    static func encodingError(forValue value: Any, codingPath: [CodingKey]) -> EncodingError {
        let context = EncodingError.Context(codingPath: codingPath, debugDescription: "Cannot encode JSONAny")
        return EncodingError.invalidValue(value, context)
    }

    static func decode(from container: SingleValueDecodingContainer) throws -> Any {
        if let value = try? container.decode(Bool.self) {
            return value
        }
        if let value = try? container.decode(Int64.self) {
            return value
        }
        if let value = try? container.decode(Double.self) {
            return value
        }
        if let value = try? container.decode(String.self) {
            return value
        }
        if container.decodeNil() {
            return JSONNull()
        }
        throw decodingError(forCodingPath: container.codingPath)
    }

    static func decode(from container: inout UnkeyedDecodingContainer) throws -> Any {
        if let value = try? container.decode(Bool.self) {
            return value
        }
        if let value = try? container.decode(Int64.self) {
            return value
        }
        if let value = try? container.decode(Double.self) {
            return value
        }
        if let value = try? container.decode(String.self) {
            return value
        }
        if let value = try? container.decodeNil() {
            if value {
                return JSONNull()
            }
        }
        if var container = try? container.nestedUnkeyedContainer() {
            return try decodeArray(from: &container)
        }
        if var container = try? container.nestedContainer(keyedBy: MyCodingKey.self) {
            return try decodeDictionary(from: &container)
        }
        throw decodingError(forCodingPath: container.codingPath)
    }

    static func decode(from container: inout KeyedDecodingContainer, forKey key: MyCodingKey) throws -> Any {
        if let value = try? container.decode(Bool.self, forKey: key) {
            return value
        }
        if let value = try? container.decode(Int64.self, forKey: key) {
            return value
        }
        if let value = try? container.decode(Double.self, forKey: key) {
            return value
        }
        if let value = try? container.decode(String.self, forKey: key) {
            return value
        }
        if let value = try? container.decodeNil(forKey: key) {
            if value {
                return JSONNull()
            }
        }
        if var container = try? container.nestedUnkeyedContainer(forKey: key) {
            return try decodeArray(from: &container)
        }
        if var container = try? container.nestedContainer(keyedBy: MyCodingKey.self, forKey: key) {
            return try decodeDictionary(from: &container)
        }
        throw decodingError(forCodingPath: container.codingPath)
    }

    static func decodeArray(from container: inout UnkeyedDecodingContainer) throws -> [Any] {
        var arr: [Any] = []
        while !container.isAtEnd {
            let value = try decode(from: &container)
            arr.append(value)
        }
        return arr
    }

    static func decodeDictionary(from container: inout KeyedDecodingContainer) throws -> [String: Any] {
        var dict = [String: Any]()
        for key in container.allKeys {
            let value = try decode(from: &container, forKey: key)
            dict[key.stringValue] = value
        }
        return dict
    }

    static func encode(to container: inout UnkeyedEncodingContainer, array: [Any]) throws {
        for value in array {
            if let value = value as? Bool {
                try container.encode(value)
            } else if let value = value as? Int64 {
                try container.encode(value)
            } else if let value = value as? Double {
                try container.encode(value)
            } else if let value = value as? String {
                try container.encode(value)
            } else if value is JSONNull {
                try container.encodeNil()
            } else if let value = value as? [Any] {
                var container = container.nestedUnkeyedContainer()
                try encode(to: &container, array: value)
            } else if let value = value as? [String: Any] {
                var container = container.nestedContainer(keyedBy: MyCodingKey.self)
                try encode(to: &container, dictionary: value)
            } else {
                throw encodingError(forValue: value, codingPath: container.codingPath)
            }
        }
    }

    static func encode(to container: inout KeyedEncodingContainer, dictionary: [String: Any]) throws {
        for (key, value) in dictionary {
            let key = MyCodingKey(stringValue: key)!
            if let value = value as? Bool {
                try container.encode(value, forKey: key)
            } else if let value = value as? Int64 {
                try container.encode(value, forKey: key)
            } else if let value = value as? Double {
                try container.encode(value, forKey: key)
            } else if let value = value as? String {
                try container.encode(value, forKey: key)
            } else if value is JSONNull {
                try container.encodeNil(forKey: key)
            } else if let value = value as? [Any] {
                var container = container.nestedUnkeyedContainer(forKey: key)
                try encode(to: &container, array: value)
            } else if let value = value as? [String: Any] {
                var container = container.nestedContainer(keyedBy: MyCodingKey.self, forKey: key)
                try encode(to: &container, dictionary: value)
            } else {
                throw encodingError(forValue: value, codingPath: container.codingPath)
            }
        }
    }

    static func encode(to container: inout SingleValueEncodingContainer, value: Any) throws {
        if let value = value as? Bool {
            try container.encode(value)
        } else if let value = value as? Int64 {
            try container.encode(value)
        } else if let value = value as? Double {
            try container.encode(value)
        } else if let value = value as? String {
            try container.encode(value)
        } else if value is JSONNull {
            try container.encodeNil()
        } else {
            throw encodingError(forValue: value, codingPath: container.codingPath)
        }
    }

    public required init(from decoder: Decoder) throws {
        if var arrayContainer = try? decoder.unkeyedContainer() {
            self.value = try JSONAny.decodeArray(from: &arrayContainer)
        } else if var container = try? decoder.container(keyedBy: MyCodingKey.self) {
            self.value = try JSONAny.decodeDictionary(from: &container)
        } else {
            let container = try decoder.singleValueContainer()
            self.value = try JSONAny.decode(from: container)
        }
    }

    public func encode(to encoder: Encoder) throws {
        if let arr = self.value as? [Any] {
            var container = encoder.unkeyedContainer()
            try JSONAny.encode(to: &container, array: arr)
        } else if let dict = self.value as? [String: Any] {
            var container = encoder.container(keyedBy: MyCodingKey.self)
            try JSONAny.encode(to: &container, dictionary: dict)
        } else {
            var container = encoder.singleValueContainer()
            try JSONAny.encode(to: &container, value: self.value)
        }
    }
}

class JSONNull: Codable {
    public init() {
    }

    public required init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        if !container.decodeNil() {
            throw DecodingError.typeMismatch(JSONNull.self, DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Wrong type for JSONNull"))
        }
    }

    public func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        try container.encodeNil()
    }
}

class MyCodingKey : CodingKey {
    let key: String

    required init?(intValue: Int) {
        return nil
    }

    required init?(stringValue: String) {
        key = stringValue
    }

    var intValue: Int? {
        return nil
    }

    var stringValue: String {
        return key
    }
}

Answer 2

Vous pouvez simplement utiliser AnyCodable type de la bibliothèque cool de Matt Thompson AnyCodable .

Eg :

import AnyCodable

struct Foo: Codable
{
    var bar: AnyCodable
}

Answer 3

J'ai résolu mon problème en créant une structure AnyValue pour permettre l'encodage et le décodage. Tous à partir de JSON :

Son utilisation est assez simple :

class MyClass: Codable {

    var data: [String: AnyValue?]?

    init(data: [String: AnyValue?]) {
        self.data = data
    }
}

let data = ["a": AnyValue(3), "b": AnyValue(true), "c": AnyValue("Rodrigo"), "d": AnyValue(3.3)]
let myClass = MyClass(data: data)

if let json = JsonUtil<MyClass>.toJson(myClass) {
    print(json) // {"data":{"d":3.3,"b":true,"c":"Rodrigo","a":3}}

    if let data = JsonUtil<MyClass>.from(json: json)?.data {
        print(data["a"]??.value() ?? "nil") // 3
        print(data["b"]??.value() ?? "nil") // true
        print(data["c"]??.value() ?? "nil") // Rodrigo
        print(data["d"]??.value() ?? "nil") // 3.3
    }
}

AnyValue struct :

struct AnyValue: Codable {

    private var int: Int?
    private var string: String?
    private var bool: Bool?
    private var double: Double?

    init(_ int: Int) {
        self.int = int
    }

    init(_ string: String) {
        self.string = string
    }

    init(_ bool: Bool) {
        self.bool = bool
    }

    init(_ double: Double) {
        self.double = double
    }

    init(from decoder: Decoder) throws {
        if let int = try? decoder.singleValueContainer().decode(Int.self) {
            self.int = int
            return
        }

        if let string = try? decoder.singleValueContainer().decode(String.self) {
            self.string = string
            return
        }

        if let bool = try? decoder.singleValueContainer().decode(Bool.self) {
            self.bool = bool
            return
        }

        if let double = try? decoder.singleValueContainer().decode(Double.self) {
            self.double = double
        }
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()

        if let anyValue = self.value() {
            if let value = anyValue as? Int {
                try container.encode(value)
                return
            }

            if let value = anyValue as? String {
                try container.encode(value)
                return
            }

            if let value = anyValue as? Bool {
                try container.encode(value)
                return
            }

            if let value = anyValue as? Double {
                try container.encode(value)
                return
            }
        }

        try container.encodeNil()
    }

    func value() -> Any? {
        return self.int ?? self.string ?? self.bool ?? self.double
    }
}

Et j'ai créé un JsonUtil struct aussi :

struct JsonUtil<T: Codable>  {

    public static func from(json: String) -> T? {
        if let jsonData = json.data(using: .utf8) {
            let jsonDecoder = JSONDecoder()

            do {
                return try jsonDecoder.decode(T.self, from: jsonData)

            } catch {
                print(error)
            }
        }

        return nil
    }

    public static func toJson(_ obj: T) -> String? {
        let jsonEncoder = JSONEncoder()

        do {
            let jsonData = try jsonEncoder.encode(obj)
            return String(data: jsonData, encoding: String.Encoding.utf8)

        } catch {
            print(error)
            return nil
        }
    }
}

Si vous avez besoin d'un nouveau type comme [Chaîne] par exemple, il suffit de l'ajouter sur Toute valeur struct.

Bonne chance :)

Answer 4

Vous pouvez essayer BeyovaJSON

import BeyovaJSON

struct Foo: Codable {
  let bar: JToken
}

let foo = try! JSONDecoder().decode(Foo.self, from: data)