parsing - Parse json in Swift, AnyObject type

Question

I'm trying to parse a json but I have some difficulties with the data types and notably the AnyObject type + downcasting.

Let's consider the following json (it's an extract of a full json).

{  "weather":
   [
      {
         "id":804,
         "main":"Clouds",
         "description":"overcast clouds",
         "icon":"04d"
      }
   ],
}

To me, the json can be described as follow :

- json: Dictionary of type [String: AnyObject] (or NSDictionary, so = [NSObject, AnyObject] in Xcode 6 b3)
    - "weather": Array of type [AnyObject] (or NSArray)
         - Dictionary of type [String: AnyObject] (or NSDictionary, so = [NSObject, AnyObject] in Xcode 6 b3)

My json is of type AnyObject! (I use JSONObjectWithData to get the JSON from a URL).

I then want to access the weather Dictionary. Here is the code I wrote.

var localError: NSError?
var json: AnyObject! = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: &localError)

if let dict = json as? [String: AnyObject] {
 if let weatherDictionary = dict["weather"] as? [AnyObject] {
      // Do stuff with the weatherDictionary
    }
}

Here is the error I got

Playground execution failed: error: <EXPR>:28:56: error: '[AnyObject]' is not a subtype of '(String, AnyObject)'
        if let weatherDictionary = dict["weather"] as? [AnyObject] {

I don't understand why dict["weather"] is compared to a subtype of (String, AnyObject) and not AnyObject.

I declared my dictionary as [String: AnyObject], so I i access a value using the String key, I should have an AnyObject, no ?

If I use NSDictionary instead of [String: AnyObject], it works.

If I use NSArray instead of [AnyObject], it works.

- The Xcode 6 beta 3 release notes tell that "NSDictionary* is now imported from Objective-C APIs as [NSObject : AnyObject].".
- And the Swift book: "When you bridge from an NSArray object to a Swift array, the resulting array is of type [AnyObject]."

EDIT

I forgot to force unwrapping the dict["weather"]!.

if let dict = json as? [String: AnyObject] {
    println(dict)
       if let weatherDictionary = dict["weather"]! as? [AnyObject] {
            println("
Weather dictionary:

(weatherDictionary)")
            if let descriptionString = weatherDictionary[0]["description"]! as? String {
                println("
Description of the weather is: (descriptionString)")
        }
    }
}

Note that we should double check for the existence of the first Optional.

if let dict = json as? [String: AnyObject] {
    for key in ["weather", "traffic"] {
        if let dictValue = dict[key] {
            if let subArray = dictValue as? [AnyObject] {
                println(subArray[0])
            }
        } else {
            println("Key '(key)' not found")
        }
    }
}

question from:https://stackoverflow.com/questions/24671249/parse-json-in-swift-anyobject-type