title: Decode JSON Data on Swift 4 returns nil
body: <p>I'm trying to decode my json data with below function. I had different Json format at first and It was working but whenI change json format, It started not to work. I try to do changes also in Structure code but nothing worked. What Am I missing? (Code is for first Json format so It needs to be work on second format too)</p>
  
  <p>First JSON:</p>
  
  <pre><code>{
  "status": 200,
  "results": [
      {
          "group_matched": false,
          "distance_mi": 4,
          "content_hash": "1rT2lirUapfrYIYxSR2u0GtmRSLPsVki9kFj4ugs8JIq6",
          "common_friends": [],
          "common_likes": [],
          "common_friend_count": 0,
          "common_like_count": 0,
          "connection_count": 0,
          "_id": "5a2805ba779f34267d32d8b0",
          "bio": "",
              "birth_date": "1997-12-09T16:28:29.761Z",
              "name": "John", 
          },
  </code></pre>
  
  <p>Second JSON:</p>
  
  <pre><code>{
      "meta": {
          "status": 200
      },
      "data": {
          "results": [
              {
                  "type": "user",
                  "user": {
                      "_id": "545001b33bf179416a30bf7f",
                      "bio": "Ä°nstagram:",
                      "birth_date": "1992-12-09T17:12:49.957Z",
                      "name": "",
                      "photos": [
                          {
                              "id": "2eb1beec-6180-4d58-90fd-5f076da96af9",
                              "url": "",
                              "processedFiles": [
                                  {
                                      "url": "",
                                      "height": 640,
                                      "width": 640
                                  },
                                  {
                                      "url": "",
                                      "height": 320,
                                      "width": 320
                                  },
                                  {
                                      "url": "",
                                      "height": 172,
                                      "width": 172
                                  },
                                  {
                                      "url": "",
                                      "height": 84,
                                      "width": 84
                                  }
                              ]
                          },
                          {
                              "id": "89d2bc07-d244-457b-b610-26ecd4e9e86d",
                              "url": "",
                              "processedFiles": [
                                  {
                                      "url": "",
                                      "height": 640,
                                      "width": 640
                                  },
                                  {
                                      "url": "",
                                      "height": 320,
                                      "width": 320
                                  },
                                  {
                                      "url": "",
                                      "height": 172,
                                      "width": 172
                                  },
                                  {
                                      "url": "",
                                      "height": 84,
                                      "width": 84
                                  }
                              ]
                          },
                          {
                              "id": "0fcafc7e-d6e7-4cc5-891a-735971d6a5b2",
                              "url": "",
                              "processedFiles": [
                                  {
                                      "url": "",
                                      "height": 640,
                                      "width": 640
                                  },
                                  {
                                      "url": "g",
                                      "height": 320,
                                      "width": 320
                                  },
                                  {
                                      "url": "",
                                      "height": 172,
                                      "width": 172
                                  },
                                  {
                                      "url": "",
                                      "height": 84,
                                      "width": 84
                                  }
                              ]
                          },
                          {
                              "id": "bac74531-09e7-4c5b-ac6c-cab36c4be587",
                              "url": "",
                              "processedFiles": [
                                  {
                                      "url": "",
                                      "height": 640,
                                      "width": 640
                                  },
                                  {
                                      "url": "",
                                      "height": 320,
                                      "width": 320
                                  },
                                  {
                                      "url": "",
                                      "height": 172,
                                      "width": 172
                                  },
                                  {
                                      "url": "",
                                      "height": 84,
                                      "width": 84
                                  }
                              ]
                          },
                          {
                              "id": "3c216244-946a-4c58-8670-cc12c05801cb",
                              "url": "",
                              "processedFiles": [
                                  {
                                      "url": "",
                                      "height": 640,
                                      "width": 640
                                  },
                                  {
                                      "url": "",
                                      "height": 320,
                                      "width": 320
                                  },
                                  {
                                      "url": "",
                                      "height": 172,
                                      "width": 172
                                  },
                                  {
                                      "url": "",
                                      "height": 84,
                                      "width": 84
                                  }
                              ]
                          },
                          {
                              "id": "-8672-488d-8b7e-f30b4560c56b",
                              "url": "",
                              "processedFiles": [
                                  {
                                      "url": "",
                                      "height": 640,
                                      "width": 640
                                  },
                                  {
                                      "url": "",
                                      "height": 320,
                                      "width": 320
                                  },
                                  {
                                      "url": "",
                                      "height": 172,
                                      "width": 172
                                  },
                                  {
                                      "url": "",
                                      "height": 84,
                                      "width": 84
                                  }
                              ]
                          }
                      ],
                      "gender": 1,
  </code></pre>
  
  <p>Struct Code:</p>
  
  <pre><code>    struct Photo: Codable{
      var url: String?
      var processedFiles: [processedFiles]?
  }
  struct User: Codable{
      var group_matched: Bool?
      var distance_mi: Int?
      var common_friend_count: Int?
      var name:String?
      var profile_picture: String?
      var instagram_id: String?
      var photos: [Photo]?
  }
  class Results : Codable {
      var results: [User] = []
      static let sharedResults = Results()
      private init() { }
      var type: String?
  
      func populateData(sender: Results){
          print(sender)
          results += sender.results
      }
  }
  </code></pre>
  
  <p>Decode Code:</p>
  
  <pre><code> let jsonData = JSON(data: response.data!)
                  let jsonData2 = try? JSONSerialization.data(withJSONObject: jsonData["data"].object)
                  print(JSON(data: jsonData2!))
  
                  let decoder = JSONDecoder()
                  var response_class = Results.sharedResults
                  response_class = try decoder.decode(Results.self, from: jsonData2!)
                  Results.sharedResults.populateData(sender: response_class)
  </code></pre>
  
  <p>EDIT: I edit second JSON, It now has array of array. How Can I implement decoder keys for that second array?</p>