Using a generic struct to represent a top level object for JSON response for Swift 4's Codable protocol

CustomCodable.playground

import UIKit

let jsonDataEnclosed = """
  { "data" :
    {
      "name": "Monalisa Octocat",
      "email": "support@github.com",
      "date": "2011-04-14T16:00:49Z"
    }
  }
  """.data(using: .utf8)!

struct ResponseData<T: Codable>: Codable {
  let data: T
}

struct Author : Codable {
  let name: String
  let email: String
  let date: Date
}

let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601

let response = try decoder.decode(ResponseData<Author>.self, from: jsonDataEnclosed)
let author = response.data
print(author.name)