In Swift, check if a key exists in JSON - json

Question

I have the following function. It is supposed to take the current song playing information from the API webpage. When a song is playing, the page says:
{ "artist" : "Artist", "song" : "Song" }
When no data is available (No song is playing):
{ "error" : "no song metadata provided" }
Is there a way to check if the "error" key exists? Or what can I do with this issue?
func songNowPlaying() {
let endpoint = NSURL(string: "http://api.vicradio.org/songs/current")
let jsonData = NSData(contentsOfURL: endpoint!)
do {
let parsed = try NSJSONSerialization.JSONObjectWithData(jsonData!, options: NSJSONReadingOptions.MutableContainers) as! NSMutableArray
SongNowText.text = parsed.valueForKey("song").componentsJoinedByString("")
ArtistNowText.text = parsed.valueForKey("artist").componentsJoinedByString("")
}
catch let error as NSError {
print("\(error)")
}
}

Answer 1

The URL returns a JSON dictionary not an array. You can check for both cases this way
func songNowPlaying() {
let endpoint = NSURL(string: "http://api.vicradio.org/songs/current")
if let jsonData = NSData(contentsOfURL: endpoint!) {
do {
let parsed = try NSJSONSerialization.JSONObjectWithData(jsonData, options: .MutableContainers) as! [String:String]
if let error = parsed["error"] {
print("Result error: \(error)")
} else {
if let song = parsed["song"] {
SongNowText.text = song
}
if let artist = parsed["artist"] {
ArtistNowText.text = artist
}
}
}
catch let error as NSError {
print("Serialization error: \(error)")
}
}
}
as the JSON object can be downcasted to [String:String] any further downcasting is not needed.