使用Codable解码JSON时可以吗? [英] Any when decoding JSON with Codable?
本文介绍了使用Codable解码JSON时可以吗?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
使用Swift 3 JSONSerialization，如果您的数据模型的一部分是完全动态的，则始终可以将反序列化的数据保留在Any处，并让使用者处理它.
With Swift 3 JSONSerialization, if a part of your data model was completely dynamic, you could always just leave the deserialized data at Any and let the consumer deal with it.
使用Swift 4的Codable，我想这样做:
With Swift 4's Codable, I'd like to do this:
struct Foo : Codable {
let bar: Any;
}
但是我明白了
JSONPlayground.playground:4:9: note: cannot automatically synthesize 'Decodable' because 'Any' does not conform to 'Decodable'
let bar: Any;
^
如果我可以实现自己的Decodable，那将不会是世界的尽头，但这将要求Decoder支持解码为Any，据我所知这还不是.例如:
That alone wouldn't be the end of the world if I could implement my own Decodable, but that would require the Decoder to support decoding to Any, which as far as I can tell it does not. For example:
extension Foo {
init(from decoder: Decoder) throws {
let container = try decoder.singleValueContainer()
let result = try container.decode(AnyClass.self)
}
}
给予
error: JSONPlayground.playground:4:36: error: cannot invoke 'decode' with an argument list of type '(AnyClass.Protocol)'
let result = try container.decode(AnyClass.self)
^
对此有什么解决办法吗?
Is there any solution to this?
推荐答案
我最终不得不实现自己的类来对Any值进行编码/解码.它虽然不漂亮，但似乎可以正常工作:
I ended up having to implement my own class to encode/decode Any values. It's not pretty, but it seems to work:
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
}
}这篇关于使用Codable解码JSON时可以吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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