How to use Any in Codable Type

Quantum Value

First of all you can define a type that can be decoded both from a String and Int value.Here it is.

enum QuantumValue: Decodable {        case int(Int), string(String)        init(from decoder: Decoder) throws {        if let int = try? decoder.singleValueContainer().decode(Int.self) {            self = .int(int)            return        }                if let string = try? decoder.singleValueContainer().decode(String.self) {            self = .string(string)            return        }                throw QuantumError.missingValue    }        enum QuantumError:Error {        case missingValue    }}

Person

Now you can define your struct like this

struct Person: Decodable {    let id: QuantumValue}

That's it. Let's test it!

JSON 1: id is String

let data = """{"id": "123"}""".data(using: String.Encoding.utf8)!if let person = try? JSONDecoder().decode(Person.self, from: data) {    print(person)}

JSON 2: id is Int

let data = """{"id": 123}""".data(using: String.Encoding.utf8)!if let person = try? JSONDecoder().decode(Person.self, from: data) {    print(person)}

UPDATE 1 Comparing values

This new paragraph should answer the questions from the comments.

If you want to compare a quantum value to an Int you must keep in mind that a quantum value could contain an Int or a String.

So the question is: what does it mean comparing a String and an Int?

If you are just looking for a way of converting a quantum value into an Int then you can simply add this extension

extension QuantumValue {        var intValue: Int? {        switch self {        case .int(let value): return value        case .string(let value): return Int(value)        }    }}

Now you can write

let quantumValue: QuantumValue: ...quantumValue.intValue == 123

UPDATE 2

This part to answer the comment left by @Abrcd18.

You can add this computed property to the Person struct.

var idAsString: String {    switch id {    case .string(let string): return string    case .int(let int): return String(int)    }}

And now to populate the label just write

label.text = person.idAsString

Hope it helps.

Codable needs to know the type to cast to.

Firstly I would try to address the issue of not knowing the type, see if you can fix that and make it simpler.

Otherwise the only way I can think of solving your issue currently is to use generics like below.

struct Person<T> {    var id: T    var name: String}let person1 = Person<Int>(id: 1, name: "John")let person2 = Person<String>(id: "two", name: "Steve")

I solved this issue defining a new Decodable Struct called AnyDecodable, so instead of Any I use AnyDecodable. It works perfectly also with nested types.

Try this in a playground:

var json = """{  "id": 12345,  "name": "Giuseppe",  "last_name": "Lanza",  "age": 31,  "happy": true,  "rate": 1.5,  "classes": ["maths", "phisics"],  "dogs": [    {      "name": "Gala",      "age": 1    }, {      "name": "Aria",      "age": 3    }  ]}"""public struct AnyDecodable: Decodable {  public var value: Any  private struct CodingKeys: CodingKey {    var stringValue: String    var intValue: Int?    init?(intValue: Int) {      self.stringValue = "\(intValue)"      self.intValue = intValue    }    init?(stringValue: String) { self.stringValue = stringValue }  }  public init(from decoder: Decoder) throws {    if let container = try? decoder.container(keyedBy: CodingKeys.self) {      var result = [String: Any]()      try container.allKeys.forEach { (key) throws in        result[key.stringValue] = try container.decode(AnyDecodable.self, forKey: key).value      }      value = result    } else if var container = try? decoder.unkeyedContainer() {      var result = [Any]()      while !container.isAtEnd {        result.append(try container.decode(AnyDecodable.self).value)      }      value = result    } else if let container = try? decoder.singleValueContainer() {      if let intVal = try? container.decode(Int.self) {        value = intVal      } else if let doubleVal = try? container.decode(Double.self) {        value = doubleVal      } else if let boolVal = try? container.decode(Bool.self) {        value = boolVal      } else if let stringVal = try? container.decode(String.self) {        value = stringVal      } else {        throw DecodingError.dataCorruptedError(in: container, debugDescription: "the container contains nothing serialisable")      }    } else {      throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Could not serialise"))    }  }}let stud = try! JSONDecoder().decode(AnyDecodable.self, from: jsonData).value as! [String: Any]print(stud)

You could extend my struct to be AnyCodable if you are interested also in the Encoding part.

Edit: I actually did it.

Here is AnyCodable

struct AnyCodable: Decodable {  var value: Any  struct CodingKeys: CodingKey {    var stringValue: String    var intValue: Int?    init?(intValue: Int) {      self.stringValue = "\(intValue)"      self.intValue = intValue    }    init?(stringValue: String) { self.stringValue = stringValue }  }  init(value: Any) {    self.value = value  }  init(from decoder: Decoder) throws {    if let container = try? decoder.container(keyedBy: CodingKeys.self) {      var result = [String: Any]()      try container.allKeys.forEach { (key) throws in        result[key.stringValue] = try container.decode(AnyCodable.self, forKey: key).value      }      value = result    } else if var container = try? decoder.unkeyedContainer() {      var result = [Any]()      while !container.isAtEnd {        result.append(try container.decode(AnyCodable.self).value)      }      value = result    } else if let container = try? decoder.singleValueContainer() {      if let intVal = try? container.decode(Int.self) {        value = intVal      } else if let doubleVal = try? container.decode(Double.self) {        value = doubleVal      } else if let boolVal = try? container.decode(Bool.self) {        value = boolVal      } else if let stringVal = try? container.decode(String.self) {        value = stringVal      } else {        throw DecodingError.dataCorruptedError(in: container, debugDescription: "the container contains nothing serialisable")      }    } else {      throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Could not serialise"))    }  }}extension AnyCodable: Encodable {  func encode(to encoder: Encoder) throws {    if let array = value as? [Any] {      var container = encoder.unkeyedContainer()      for value in array {        let decodable = AnyCodable(value: value)        try container.encode(decodable)      }    } else if let dictionary = value as? [String: Any] {      var container = encoder.container(keyedBy: CodingKeys.self)      for (key, value) in dictionary {        let codingKey = CodingKeys(stringValue: key)!        let decodable = AnyCodable(value: value)        try container.encode(decodable, forKey: codingKey)      }    } else {      var container = encoder.singleValueContainer()      if let intVal = value as? Int {        try container.encode(intVal)      } else if let doubleVal = value as? Double {        try container.encode(doubleVal)      } else if let boolVal = value as? Bool {        try container.encode(boolVal)      } else if let stringVal = value as? String {        try container.encode(stringVal)      } else {        throw EncodingError.invalidValue(value, EncodingError.Context.init(codingPath: [], debugDescription: "The value is not encodable"))      }    }  }}

You can test it With the previous json in this way in a playground:

let stud = try! JSONDecoder().decode(AnyCodable.self, from: jsonData)print(stud.value as! [String: Any])let backToJson = try! JSONEncoder().encode(stud)let jsonString = String(bytes: backToJson, encoding: .utf8)!print(jsonString)