如何使用 Codable 处理不同类型的 JSON 数据？

Question

struct Sample: Codable {
    let dataA: Info?

    enum CodingKeys: String, CodingKey {
        case dataA
    }

    enum Info: Codable {
        case double(Double)
        case string(String)

        init(from decoder: Decoder) throws {
            let container = try decoder.singleValueContainer()
            if let x = try? container.decode(Double.self) {
                self = .double(x)
                return
            }
            if let x = try? container.decode(String.self) {
                self = .string(x)
                return
            }
            throw DecodingError.typeMismatch(Info.self, DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Wrong type for Info"))
        }

        func encode(to encoder: Encoder) throws {
            var container = encoder.singleValueContainer()
            switch self {
            case .double(let x):
                try container.encode(x)
            case .string(let x):
                try container.encode(x)
            }
        }
    }
}

So, I've got some data from server as JSON and converted for my model "Sample".

As you can see, Sample.data can be String or Double .

But I don't know how I can get dataA in other class.

let foodRate = dataFromServer.dataA .....?

What should I do for using dataA ?

Answer 1

You can use a switch statement to extract the values

switch dataFromServer.dataA {
case .double(let number):
    print(number)
case .string(let string):
    print(string)
case .none:
    print("Empty")
}