Parse json item array (consists of different items) with enums & associated values

EnumJsonParsing.swift

import Foundation

struct GeometricShapes: Decodable {
    let items: [Object]
}

enum Object: Decodable {
    case square(Square)
    case sphere(Sphere)
    case cylinder(Cylinder)
    case unknown
    
    enum CodingKeys: String, CodingKey {
        case type
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        guard let type = try? container.decode(ObjectType.self, forKey: .type) else {
            self = .unknown
            return
        }
        
        let objectContainer = try decoder.singleValueContainer()
        
        switch type {
        case .square:
            let square = try objectContainer.decode(Square.self)
            self = .square(square)
        case .sphere:
            let sphere = try objectContainer.decode(Sphere.self)
            self = .sphere(sphere)
        case .cylinder:
            let cylinder = try objectContainer.decode(Cylinder.self)
            self = .cylinder(cylinder)
        case .unknown:
            self = .unknown
        }
    }
}

enum ObjectType: String, Decodable {
    case square
    case sphere
    case cylinder
    case unknown
    
    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        let type = try container.decode(String.self)
        self = ObjectType(rawValue: type) ?? .unknown
    }
}

struct Square: Decodable {
    let sideLength: Int
    
    enum CodingKeys: String, CodingKey {
        case sideLength = "side_length"
    }
}

struct Sphere: Decodable {
    let diameter: Int
}

struct Cylinder: Decodable {
    let diameter: Int
    let height: Int
}

let JSON = """
    {
        "items": [
            {
                "type": "square",
                "side_length": 12
            },
            {
                "type": "sphere",
                "diameter": 4
            },
            {
                "type": "cylinder",
                "diameter": 4,
                "height": 10
            },
            {
                "type": "lalala",
                "unknown_key": 0
            }
        ]
    }
""".data(using: .utf8)!

let decoder = JSONDecoder()
let geometricObjects = try decoder.decode(GeometricShapes.self, from: JSON)
let items = geometricObjects.items


// Here we just parse and print some values of the models.
// This is how you can parse with a wrapper enum with associated value.
items.forEach({
    switch $0 {
    case .cylinder(let cylinder):
        print("Diameter of cylinder is: \(cylinder.diameter)")
        print("Height of cylinder is: \(cylinder.height)")
    case .sphere(let sphere):
        print("Diameter of sphere is: \(sphere.diameter)")
    case .square(let square):
        print("Side length of square is: \(square.sideLength)")
    case .unknown:
        print("We have an unknown type.")
    }
})