Codable to decode required properties only from deeply nested JSON

Codable+NestedJSON.swift

import UIKit

struct Employee: Decodable {
    let name: String
    let city: String
    
    enum CodingKeys: String, CodingKey {
        case name
        case city
        case contactInformation
        case mailingAddress
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        name = try container.decode(String.self, forKey: .name)
        
        // Get container for `ContactInformation`
        let contactInformationContainer = try container.nestedContainer(keyedBy: CodingKeys.self, forKey: .contactInformation)
        
        // Get container for `MailingAddress`
        let mailingAddressContainer = try contactInformationContainer.nestedContainer(keyedBy: CodingKeys.self, forKey: .mailingAddress)
        
        // decode `city` from `MailingAddress`
        city = try mailingAddressContainer.decode(String.self, forKey: .city)
    }
}

let jsonData: Data = """
{
    "name": "Eric",
    "contactInformation": {
        "phoneNumber": "+1 123123123",
        "email": "[email protected]",
        "mailingAddress": {
            "city": "New York City",
            "state": "New York",
            "pincode": 100001
        }
    }
}
""".data(using: .utf8)!

let employee = try! JSONDecoder().decode(Employee.self, from: jsonData)
print("Employee name = \(employee.name)")
print("Employee city = \(employee.city)")