How to check if a field type Any? is nil o NSNull

Question

I'm actually trying to parse a Json object with Swift3 on Xcode8.1. This is my code:

if let objData = objJson["DATA"] as! NSDictionary? {
    var msg: String = ""
    if let tmp = objData.object(forKey: "Message") { 
        msg = tmp as! String
    } else {
        print("NIIILLLLL")
    }
}

I'm getting this error message: Could not cast value of type 'NSNull' (0x4587b68) to 'NSString' (0x366d5f4) at this line msg = tmp as! String.

I'm not understanding why I'm getting this error because the type of tmp is Any and it should display the print instead of convert tmp as! String

Thank you for the help,

Answer 1

You can add casting in let.

if let tmp = objData.object(forKey: "Message") as? String { 
    msg = tmp
}

Answer 2

With Swift 3, for example:

fileprivate var rawNull: NSNull = NSNull()
public var object: Any {
   get {
      return self.rawNull
   }
}

You can check field object as:

if self.object is NSNull {
  // nil
}