typealias Codable = Encodable & Decodablestruct Employee: Codable {    var name:String    var id: Int    var mToy:Toy}struct Toy:Codable {    var name:String}extension Employee:CustomStringConvertible {    var description: String {        return name + "(" + String(id) + "): " + mToy.name    }}        /// encode instance to jsonString        let toyA = Toy(name: "Teddy Bear")        let employeeA = Employee(name: "EmployA", id:1, mToy:toyA)        let jsonEncoder = JSONEncoder()        let jsonData = try? jsonEncoder.encode(employeeA)        // Xcode omits jsonData and only provides the number of bytes in jsonData        // jsonData contains an unreadable representation of employeeA        print("jsonData: \(jsonData)")        let jsonString = String(data: jsonData!, encoding: .utf8)        print("jsonString: \(jsonString)")                        /// decode jsonString to instance        let jsonDecoder = JSONDecoder()        let employeeADecoded = try? jsonDecoder.decode(Employee.self, from: jsonData!)        print(employeeADecoded!) //result /*

　　jsonData: Optional(54 bytes)

　　jsonString: Optional("{\"name\":\"EmployA\",\"id\":1,\"mToy\":{\"name\":\"Teddy Bear\"}}")

　　EmployA(1): Teddy Bear

*/

 

假设，现在后台改接口了

from : {\"name\":\"EmployA\",\"id\":1,\"mToy\":{\"name\":\"Teddy Bear\"}}

to : {\"name\":\"EmployA\",\"gift\":\"Teddy Bear\",\"emplyeeID\":1}

 

需要实现encoding 和 decoding的逻辑。

encode 需要实现 encode(to: Encoder) throws

decode 需要实现 init(from decoder: Decoder) throws

//typealias Codable = Encodable & Decodablestruct Employee{    var name:String    var id: Int    var mToy:Toy        enum CodingKeys: String, CodingKey{        case id = "emplyeeID"        case name        case gift    }}extension Employee: Encodable {    func encode(to encoder: Encoder) throws {        var container = encoder.container(keyedBy: CodingKeys.self)        try container.encode(name, forKey: .name)        try container.encode(id, forKey: .id)        try container.encode(mToy.name, forKey: .gift)    }}extension Employee:Decodable {    init(from decoder: Decoder) throws {        let values = try decoder.container(keyedBy: CodingKeys.self)        name = try values.decode(String.self, forKey: .name)        id = try values.decode(Int.self, forKey: .id)        let gift = try values.decode(String.self, forKey: .gift)        mToy = Toy(name: gift)    }}extension Employee:CustomStringConvertible {    var description: String {        return name + "(" + String(id) + "): " + mToy.name    }}struct Toy{    var name:String}