Decodable for JSON with two structs under the same tag

Question

I have this json:

{ \"stuff\": [
 {
 \"type\":\"car\",
 \"object\":{
  \"a\":66,
  \"b\":66,
  \"c\":66 }},
 {
 \"type\":\"house\",
 \"object\":{
  \"d\":66,
  \         


        

Answer 1

The swiftiest way in my opinion is an enum with associated types

This is valid JSON

let jsonString = """
{ "stuff": [
    {
    "type":"car",
    "object":{
        "a":66,
        "b":66,
        "c":66
        }
    },{
    "type":"house",
    "object":{
        "d":66,
        "e":66,
        "f":66
        }
    },{
    "type":"car",
    "object":{
        "a":66,
        "b":66,
        "c":66
        }
    }
]}
"""

These are the structs

struct Root : Decodable {
    let stuff : [Object]
}

enum Type : String, Decodable { case car, house }

struct Car : Decodable {
    let a, b, c : Int
}

struct House : Decodable {
    let d, e, f : Int
}


enum Object : Decodable {
    case house(House), car(Car)

    private enum CodingKeys : String, CodingKey { case type, object }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        let type = try container.decode(Type.self, forKey: .type)
        switch type {
        case .car:
            let carData = try container.decode(Car.self, forKey: .object)
            self = .car(carData)
        case .house:
            let houseData = try container.decode(House.self, forKey: .object)
            self = .house(houseData)
        }
    }
}

And the code to decode the JSON

do {
    let result = try JSONDecoder().decode(Root.self, from: Data(jsonString.utf8))
    let objects = result.stuff
    for object in objects {
        switch object {
        case .car(let car): print(car)
        case .house(let house): print(house)
        }
    }
} catch {
    print(error)
}