Decoding nested objects with dynamic keys

decode-dynamic-keys.swift

import Foundation

// JSON response converted to Data
let response = """
{
    "name": "Kilo Loco",
    "pets": {
        "0": {
            "name": "Doggo"
        },
        "1": {
            "name": "Kitty"
        }
    }
}
"""
    .data(using: .utf8)!

// Nested object type that is Codable
struct Pet: Codable {
    let name: String
}

// The object that represents the Response
struct User: Codable {
    let name: String
    let pets: [Pet]
    
    // The response is not returning an array as the
    // User object expects, so we need to manually handle
    // how the response will be decoded
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        self.name = try container.decode(String.self, forKey: .name)
        
        // We can decode anything that is Decodable, and that
        // applies to dictionaries with Decodable Keys and
        // Values
        let petsDict = try container.decode([String: Pet].self, forKey: .pets)
        self.pets = petsDict.map { $0.value }
    }
}

do {
    // Decode as usual
    let user = try JSONDecoder().decode(User.self, from: response)
    print(user)
    
} catch {
    print(error)
}

This helped me a lot. Thank you.