title: NSDictionary, (key:AnyObject, value:AnyObject) does not have a member name subscript
body: <p>I am learning swift for IOS , while I was doing tour on youtube (Swift: Using External Databases and API's by Skip Wilson )for external database, I found the part:</p>
  
  <pre><code>service = PostService()
      service.getPosts {
          (response) in
          self.loadPosts(response["posts"]! as NSDictionary)
      }
  
  func loadPosts(posts:NSDictionary) {
          for post in posts {
              var id = (post["Post"]["id"] as String)
              var title = post["Post"]!["title"]! as String
              var author = post["Post"]!["author"]! as String
              var content = post["Post"]!["content"]! as String
              var postObj = Post(id: id, title: title, author: author, content: content)
             postsCollection.append(postObj)
          }
          dispatch_async(dispatch_get_main_queue()) {
              self.tableView.reloadData()
          }
      }
  </code></pre>
  
  <p>Originally the NSDictionary here was NSArray, but its not working since NSArray only takes int for key now, and PostService.getPost() return the type NSDictionary. So I changed it to NSDictionary.</p>
  
  <p>However, all of the var id,title, author ,content  has appear error </p>
  
  <pre><code>(key:AnyObject, value:AnyObject) does not have a member name subscript
  </code></pre>
  
  <p>it seems that I need to declare the key and value to be &lt; String , String> ,but I am not sure now to do this. 
  Blow is code for Postservice:</p>
  
  <pre><code>class PostService {
  
      var settings:Settings!
  
      init(){
          self.settings = Settings()
      }
  
      func getPosts(callback:(NSDictionary)-&gt;()) {
          println("get posts")
          request(settings.viewPosts,callback)
      }
  
      func request(url:String,callback:(NSDictionary)-&gt;()) {
          var nsURL = NSURL(string: url)
          println(callback)
          let task = NSURLSession.sharedSession().dataTaskWithURL(nsURL!) {
              (data,response,error) in
              var error:NSError?
              var response = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: &amp;error) as NSDictionary
                        callback(response)
          }
          task.resume()
      }
  }
  </code></pre>
  
  <p>I know this could be a very simple and silly question, but I still cant figure it out after searching on google. What should I do? Any assistance will be highly appreciated.</p>