Cannot play album with AVAudioPlayer - macos

Question

I'm working on a very simple OSX application that will allow me to play either a song or a folder of songs.
I can choose a song and play it and everything is fine. I can choose a folder and create an array of songs and... play the last one.
var currentSong: NSURL?
var album: [NSURL] = []
var audioPlayer = AVAudioPlayer()
My playing function is
func playCurrent(){
do {
try audioPlayer = AVAudioPlayer(contentsOfURL: currentSong!)
} catch {
print("Ignoring errors for now")
}
audioPlayer.play()
}
This works fine whenever I set currentSong to a NSURL. I choose one song, it plays it.
My album function is as follows:
#IBAction func chooseAlbumAndPlay(sender: AnyObject) {
album = albumFromFile()
for song in album {
currentSong = song
playCurrent()
}
}
and here I have the problem. albumFromFile opens an NSOpenPanel, lets me choose a folder, and dumps paths to playable items into an array of NSURLs. This part works, I've verified it, so I really have an array with 12 or 20 or whatever correct, playable URLs. If I just run it as is, only the last song in any album gets played. If I set a breakpoint in the playCurrent() function, I can hear that it will actually play a tiny snippet - less than a note in most cases - of all songs but the last.
According to the documentation, play() returns a boolean - and it will happily report that it has finished playing every song in this loop.
My - human - opinion is that a song has only finished playing when I have heard all of it.
If I query the duration of the current AVAudioPlayer, they all report perfectly reasonable-sounding values.
I'm completely stumped here. PlayCurrent seems to completely fail to assert itself as a running function. The expected behaviour is that it will not exit until play() has finished playing; observed behaviour is that it will touch every song for the briefest time, go 'been there' and return to the enclosing loop.
How can I force AVAudioPlayer to play the whole of a file before exiting my playCurrent() function? And where would I have found that information? (The class documentation is unhelpful, the mentioned audio guides do not exist - right now, the Developer Library does not mention any basic audio guides for OSX.

Answer 1

The answer is, once you get around to it, very obvious indeed. Unfortunately, the documentation really is no help at all. I could, in theory, have found the solution by looking at the entry for AVAudioPlayer in the AVFoundationFramework reference, but I didn't. (I found it by wildly casting about and a chance mention).
There appear to be no working OSX examples; Apple's iOS example uses the MediaPlayer framework that is not available on OSX.
The solution is as follows:
An AVAudioPlayer plays a single sound.
If you want to play more than one sound, you need an AVQueuePlayer which can also play a single sound from a URL or a queue of AVPlayerItems (this class has an init(URL:) method).
If anyone has an idea why AVAudioPlayer behaves as it does, I'm still interested to hear it.