json_decoding.swift

// Decoding JSON

// A JSON string
let data = ...

// We create an optional type which is nil to begin with.
var parseError: NSError?

// We parse the JSON, passing the nil parseError by reference. It will be set to
// an instance of NSError if anything goes wrong.
let parsedObject: AnyObject? = NSJSONSerialization.JSONObjectWithData(data,
  options: NSJSONReadingOptions.AllowFragments,
  error: &parseError)

// Now the madness begins. Each one of these conditionals is checking that the
// value being requested exists and is of the type being asked of it.
if let topApps = parsedObject as? NSDictionary {
  if let feed = topApps["feed"] as? NSDictionary {
    if let apps = feed["entry"] as? NSArray {
      if let firstApp = apps[0] as? NSDictionary {
        if let imname = firstApp["im:name"] as? NSDictionary {
          if let appName = imname["label"] as? NSString {
            println("The app name is: \(appName!)")
          }
        }
      }
    }
  }
}