JSONDecoder 解码不同类型的相同

Question

I'm using JSONDecoder to parse my JSON response:

{"status":"1","errorCode":"0","msg":"","info":1}

or

{"status":"1","errorCode":"0","msg":"","info":"a"}

or

{"status":"1","errorCode":"0","msg":"","info":{"name":"a"}}

or

{"status":"1","errorCode":"0","msg":"","info":{"text":"b"}}

or

{"status":"1","errorCode":"0","msg":"","info":[{"name":"a"}]}

Here is my basejson

import Foundation

class BaseJson: Decodable {
    var id = UUID()
    var status: String
    var errorCode: String
    var msg: String

    private enum CodingKeys: String, CodingKey {
        case status = "status", errorCode = "errorCode", msg = "msg", info = "info"
    }

    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        status = try container.decodeIfPresent(String.self, forKey: .status) ?? "0"
        errorCode = try container.decodeIfPresent(String.self, forKey: .errorCode) ?? "0"
        msg = try container.decodeIfPresent(String.self, forKey: .msg) ?? "1"
    }
}

So what should I do to make this basic class parse all the results

Answer 1

You can use a Enum with associated value to handle that.

But as said by vadian, if you can, it's better that the API responds always the same kind of data according to the same parameters.

You can add this:

enum Info: Decodable {

    enum DecodingError: Error {
        case unknownValueType
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        if let asInt = try? container.decode(Int.self) {
            self = .intValue(asInt)
        } else if let asString = try? container.decode(String.self) {
            self = .stringValue(asString)
        } else if let asDict = try? container.decode([String: String].self) {
            self = .dictValue(asDict)
        } else if let asArrayofDicts = try? container.decode([[String: String]].self) {
            self = .arrayOfDictValue(asArrayofDicts)
        } else {
            throw Info.DecodingError.unknownValueType
        }
    }

    case intValue(Int)
    case stringValue(String)
    case dictValue([String: String])
    case arrayOfDictValue([[String: String]])
}

I used [String: String] and [[String: String]] , but if that's limited you can also put your own custom struct:

struct InfoText: Decodable { let text: String }

struct InfoName: Decodable { let name: String }

and do:

case infoText(InfoText)

if let asInfoText = try? container.decode(InfoText.self) {... }

etc.

Full code and text (copy pastable in Plyagrounds):

class BaseJson: Decodable {

    enum Info: Decodable {

        enum DecodingError: Error {
            case unknownValueType
        }

        init(from decoder: Decoder) throws {
            let container = try decoder.singleValueContainer()
            if let asInt = try? container.decode(Int.self) {
                self = .intValue(asInt)
            } else if let asString = try? container.decode(String.self) {
                self = .stringValue(asString)
            } else if let asDict = try? container.decode([String: String].self) {
                self = .dictValue(asDict)
            } else if let asArrayofDicts = try? container.decode([[String: String]].self) {
                self = .arrayOfDictValue(asArrayofDicts)
            } else {
                throw Info.DecodingError.unknownValueType
            }
        }

        case intValue(Int)
        case stringValue(String)
        case dictValue([String: String])
        case arrayOfDictValue([[String: String]])
    }

    var id = UUID()
    var status: String
    var errorCode: String
    var msg: String
    var info: Info

    private enum CodingKeys: String, CodingKey {
        case status = "status", errorCode = "errorCode", msg = "msg", info = "info"
    }

    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        status = try container.decode(String.self, forKey: .status)
        errorCode = try container.decode(String.self, forKey: .errorCode)
        msg = try container.decode(String.self, forKey: .msg)
        info = try container.decode(Info.self, forKey: .info)
    }

    static func test() {
        let jsonStr = """
[
{"status":"1","errorCode":"0","msg":"","info":1},
{"status":"1","errorCode":"0","msg":"","info":"a"},
{"status":"1","errorCode":"0","msg":"","info":{"name":"a"}},
{"status":"1","errorCode":"0","msg":"","info":{"text":"b"}},
{"status":"1","errorCode":"0","msg":"","info":[{"name":"a"}]}
]
"""

        let jsonData = jsonStr.data(using: .utf8)!

        do {
            let bases = try JSONDecoder().decode([BaseJson].self, from: jsonData)
            print(bases)

            for aBase in bases {
                var infoStr = ""
                switch aBase.info {
                case .arrayOfDictValue(let array):
                    infoStr = "\(array)"
                case .dictValue(let dictt):
                    infoStr = "\(dictt)"
                case .intValue(let intV):
                    infoStr = "\(intV)"
                case .stringValue(let str):
                    infoStr = str
                }
                print("Got: \(aBase.id), status: \(aBase.status), errorCode: \(aBase.errorCode), msg: \(aBase.msg), info: \(aBase.info) - badStringConversion for understanding: \(infoStr)")
            }
        } catch {
            print("Error: \(error)")
        }
    }
}

BaseJson.test()

Output:

$> [__lldb_expr_75.BaseJson, __lldb_expr_75.BaseJson, __lldb_expr_75.BaseJson, __lldb_expr_75.BaseJson, __lldb_expr_75.BaseJson]
$> Got: C92A4315-413C-4DA3-9D0B-E6CE3B081AF3, status: 1, errorCode: 0, msg: , info: intValue(1) - badStringConversion for understanding: 1
$> Got: 1AB9FE74-E282-4AC9-97B1-814DD5C9F412, status: 1, errorCode: 0, msg: , info: stringValue("a") - badStringConversion for understanding: a
$> Got: F082FD0D-818D-4A6F-906A-3A80D911C2BA, status: 1, errorCode: 0, msg: , info: dictValue(["name": "a"]) - badStringConversion for understanding: ["name": "a"]
$> Got: 2424AFD2-8417-4FCB-B97A-D03AB30A9C45, status: 1, errorCode: 0, msg: , info: dictValue(["text": "b"]) - badStringConversion for understanding: ["text": "b"]
$> Got: 05DDB7CB-DD0E-41BB-B878-F1AEBF0D6F43, status: 1, errorCode: 0, msg: , info: arrayOfDictValue([["name": "a"]]) - badStringConversion for understanding: [["name": "a"]]