Convert a callback Swift JSON AnyObject into a NSDictionary

Question

I have a network connection with reads the data using JSON and gives a callback;

executeRequestURL(requestURL: url, taskCallback: {(status, resp) -> Void in

            if (status == true) {
                if let results = resp as? NSDictionary {
                    print ("\(results.count) results found")
                    let list = results.allValues.first as! NSArray

                    print (list)
                }

            } else {
                print ("Error -- \(resp)")
            }
        })

This calls;

private class func executeRequestURL(requestURL: NSURL, taskCallback: @escaping (Bool, AnyObject?) -> ()) {
        print ("Attempting URL -- \(requestURL)")

        let request: NSURLRequest = NSURLRequest(url: requestURL as URL, cachePolicy: .reloadIgnoringLocalAndRemoteCacheData, timeoutInterval: kAPI_TIMEOUT)

        let session: URLSession = URLSession.shared


        let task = session.dataTask(with: request as URLRequest, completionHandler: {
            (data, response, error) in

            guard error == nil else {
                print(error)
                return
            }
            guard let data = data else {
                print("Data is empty")
                return
            }

            let json = try! JSONSerialization.jsonObject(with: data, options: [])
            //print(json)

            if let response = response as? HTTPURLResponse , 200...299 ~= response.statusCode {
                taskCallback(true, json as AnyObject?)
            } else {
                taskCallback(false, json as AnyObject?)
            }

        })
        task.resume()
    }

The problem I have is that I want to read the results into a dictionary, loop through it and create objects.

For now, I will put my code in the executeRequestURL just to ensure it works, but I intend to seperate this code away for the required entity.

Question:

How do I read the resp as a dictionary?

Thanks

Sample response follows;

{
  "objects": [
    {
      "uid": "coll_20ce39424470457c925f823fc150b3d4",
      "title": "Popular",
      "temp_image": "",
      "body": "",
      "active": true,
      "slug": "popular",
      "created": "2014-10-25T12:45:54+00:00",
      "modified": "2014-10-25T12:45:54.159000+00:00",
      "ends_on": "2100-01-01T00:00:00+00:00",
    }
  ]
}

Answer 1

As the JSON is a dictionary, return a dictionary ([String:Any]) from the callback. In Swift 3 AnyObject has become Any. The strong type system of Swift encourages to be always as specific as possible.

Do a better error handling! You should return an error rather than just false.

The code uses the new Swift 3 structs URL and URLRequest

private class func executeRequestURL(requestURL: URL, taskCallback: @escaping (Bool, [String:Any]?) -> ()) {
  print ("Attempting URL -- \(requestURL)")

  let request = URLRequest(url: requestURL, cachePolicy: .reloadIgnoringLocalAndRemoteCacheData, timeoutInterval: kAPI_TIMEOUT)

  let session = URLSession.shared


  let task = session.dataTask(with: request, completionHandler: {
    (data, response, error) in

    guard error == nil else {
      print(error)
      taskCallback(false, nil)
      return
    }
    guard let data = data else {
      print("Data is empty")  // <- this will never be reached. If there is no error,
      taskCallback(false, nil) // data is always non-nil.
      return
    }
    if let response = response as? HTTPURLResponse , 200...299 ~= response.statusCode {
      let json = try! JSONSerialization.jsonObject(with: data, options: []) as!  [String:Any]
      taskCallback(true, json)
    } else {
      taskCallback(false, nil)
    }
  })
  task.resume()
}

The JSON result contains a dictionary with one key objects which contains an array of dictionaries. JSON collection types are very easy to distinguish: {} is dictionary, [] is array.

---

To map the JSON to objects create a struct

struct Item {

  var uid : String
  var title : String
  var tempImage : String
  var body : String
  var active : Bool
  var slug : String
  var created : String
  var modified : String
  var endOn : String
}

and an array

var items = [Item]()

Then map the dictionaries to Item

if let objects = json["objects"] as? [[String:Any]] {
  for object in objects {
    let uid = object["uid"] as! String
    var title = object["title"] as! String
    var tempImage = object["temp_image"] as! String
    var body = object["body"] as! String
    var active = object["active"] as! Bool
    var slug = object["slug"] as! String
    var created = object["created"] as! String
    var modified  = object["modified"] as! String
    var endOn  = object["end_on"] as! String
    let item = Item(uid: uid, title: title, tempImage:tempImage, body: body, active: active, slug: slug, created: created, modified: modified, endOn: endOn)
    items.append(item)

  }

The JSON values seem to come from a database which includes always all fields so the forced unwrapped values are safe.