A little extension to easily decode date with custom formats

Decodable+CustomDateFormat.swift

import Foundation

var json = """
{
"lastSyncDate": "2018-10-28T09:03:59+0000",
"posts": [
{
"id": 0,
"title": "Swift 4 Codable: tips and tricks",
"link": "https://medium.com/@MarioIannotta/swift-4-codable-tips-and-tricks-7ab4674736d2",
"publicationDate": "23/09/2018"
},
{
"id": 1,
"title": "Handle swift logs and testing safely and painless",
"link": "https://medium.com/@MarioIannotta/handle-swift-test-and-log-safely-c825d6006bc4",
"publicationDate": "22/08/2016"
}
]
}

"""


extension KeyedDecodingContainer where Key: CodingKey {
    
    func decodeDate(from key: Key, format: String) throws -> Date? {
        let dateAsString = try decode(String.self, forKey: key)
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = format
        return dateFormatter.date(from: dateAsString)
    }
    
}

struct PostsServiceResponse: Decodable {
    
    struct Post: Decodable {
        
        enum CodingKeys: String, CodingKey {
            case id
            case title
            case link
            case publicationDate
        }
        
        let id: Int
        let title: String
        let link: String
        let publicationDate: Date?
        
        public init(from decoder: Decoder) throws {
            let container = try decoder.container(keyedBy: CodingKeys.self)
            id = try container.decode(Int.self, forKey: .id)
            title = try container.decode(String.self, forKey: .title)
            link = try container.decode(String.self, forKey: .link)
            publicationDate = try container.decodeDate(from: .publicationDate, format: "dd/MM/yyyy")
        }
        
    }
    
    enum CodingKeys: String, CodingKey {
        case lastSyncDate
        case posts
    }
    
    let lastSyncDate: Date?
    let posts: [Post]
    
    public init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        lastSyncDate = try container.decodeDate(from: .lastSyncDate, format: "yyyy-MM-dd'T'HH:mm:ssZ")
        posts = try container.decode([Post].self, forKey: .posts)
    }
    
}

let data = json.data(using: .utf8) ?? Data()
let jsonDecoder = JSONDecoder()
let postsServiceResponse = try? jsonDecoder.decode(PostsServiceResponse.self, from: data)
print(postsServiceResponse.debugDescription)