Building a wether app

lazy var config: NSURLSessionConfiguration = NSURLSessionConfiguration.defaultSessionConfiguration()
lazy var session: NSURLSession = NSURLSession(configuration: self.config)
let queryURL: NSURL

typealias JSONDictionaryCompletion = ([String: AnyObject]?) -> Void

init(url: NSURL) {
    self.queryURL = url
}

func downloadJSONFromURL(completion: JSONDictionaryCompletion) {

    let request: NSURLRequest = NSURLRequest(URL: queryURL)
    let dataTask = session.dataTaskWithRequest(request) {
        (let data, let response, let error) in

        // 1. Check HTTP response for successful GET request

        if let httpResponse = response as? NSHTTPURLResponse {

            switch(httpResponse.statusCode) {
            case 200:
                // 2. Create JSON object with data
                do {
                    let jsonDictionary = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as! [String: AnyObject]
                    completion(jsonDictionary)
                } catch let error {
                    print("JSON Serialization failed. Error: \(error)")
                }
            default:
                print("GET request not successful. HTTP status code: \(httpResponse.statusCode)")
            }

        } else {
            print("Error: Not a valid HTTP response")
        }
    }
}