在带有继承的Swift 4中使用Decodable

Question

使用类继承是否会破坏类的可解码性。例如下面的代码

class Server : Codable {

    var id : Int?

}

class Development : Server {

    var name : String?

    var userId : Int?

}

var json = "{\"id\" : 1,\"name\" : \"Large Building Development\"}"

let jsonDecoder = JSONDecoder()

let item = try jsonDecoder.decode(Development.self, from:json.data(using: .utf8)!) as Development

print(item.id ?? "id is nil")

print(item.name ?? "name is nil") here

输出为：

1

name is nil

现在，如果我将其反转，则名称会解码，而id不会。

class Server {

    var id : Int?

}

class Development : Server, Codable {

    var name : String?

    var userId : Int?

}

var json = "{\"id\" : 1,\"name\" : \"Large Building Development\"}"

let jsonDecoder = JSONDecoder()

let item = try jsonDecoder.decode(Development.self, from:json.data(using: .utf8)!) as Development

print(item.id ?? "id is nil")

print(item.name ?? "name is nil")

输出为：

id is nil

Large Building Development

而且您不能在两个类中都表示Codable。

Answer 1

override func encode(to encoder: Encoder) throws {    try super.encode(to: encoder)    var container = encoder.container(keyedBy: CodingKeys.self)    try container.encode(employeeID, forKey: .employeeID)}对于解码，我这样做： required init(from decoder: Decoder) throws {    try super.init(from: decoder)    let values = try decoder.container(keyedBy: CodingKeys.self)    total = try values.decode(Int.self, forKey: .total)  }private enum CodingKeys: String, CodingKey{    case total}