translate Objective-C to Swift NSNotificationCenter

I have the following Objective-C code from webpage https://developer.apple.com/library/ios/documentation/Audio/Conceptual/iPodLibraryAccess_Guide/UsingMediaPlayback/UsingMediaPlayback.html

NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];

[notificationCenter

addObserver: self

selector: @selector (handle_NowPlayingItemChanged:)

name: MPMusicPlayerControllerNowPlayingItemDidChangeNotification

object: musicPlayer];

[notificationCenter

addObserver: self

selector: @selector (handle_PlaybackStateChanged:)

name: MPMusicPlayerControllerPlaybackStateDidChangeNotification

object: musicPlayer];

[musicPlayer beginGeneratingPlaybackNotifications];

I need to translate the code to Swift.

I was able to translate the first line into:

var notificationCenter: NSNotificationCenter = NSNotificationCenter.defaultCenter()

When I translated the second statement, I have the following so far, which Xcode filled in for me:

notificationCenter.addObserver(<#T##observer: AnyObject##AnyObject#>, selector: <#T##Selector#>, name: <#T##String?#>, object: <#T##AnyObject?#>)

I need help with this part.

I believe I should use "self" as the first argument. How do I know what to use as the second argument?

Could someone translate the rest of the code for me?