swift - Looping through music -

i have app want cycle through music. play 15 secs of song move on next one.

i have struct (musiclibrary) holds array of song information (a struct called songitem) including persistentid of songs on iphone. struct working , if print out names of songs works. (structs @ bottom of post)

i have function (playthesong) uses persistentid have stored in songs object mpmusicplayercontroller - part of mediaplayer library.

what happens when button pressed first song starts play. song persistentids printed debugger output , not sure why. after 15 seconds first song stops - added timer in attempt move onto next song, here doesn't work. think because loop through song structs executing , problem.

i know doing silly here, can't put finger on it.

note: work on phone simulator doesn't have music library.

this viewcontroller.

import uikit import mediaplayer  class runningmusicviewcontroller: uiviewcontroller {     var mymusic = musiclibrary()      let mymusicplayer = mpmusicplayercontroller()      var timer: int = 15     var clock = nstimer()      override func viewdidload() {         super.viewdidload()     }      override func didreceivememorywarning() {         super.didreceivememorywarning()         // dispose of resources can recreated.     }      @ibaction func startmusicbutton(sender: anyobject) {          // first song of our quiz , play - use persistent id.         let songs = mymusic.getsongs()         let totalsongs = songs.count          clock = nstimer.scheduledtimerwithtimeinterval(1.0, target: self, selector: "countdown", userinfo: nil, repeats: true)          index in 0..<totalsongs {              playthesong(songs, index: index)           }      }       func playthesong(songsinquiz: [songitem], index:int) {         let songtoplay: songitem = songsinquiz[index]         print("song id=" + string(songtoplay.persistentid))         let predicate = mpmediapropertypredicate(value: int(songtoplay.persistentid), forproperty: mpmediaitempropertypersistentid)         let songquery = mpmediaquery()         songquery.addfilterpredicate(predicate)         mymusicplayer.setqueuewithitemcollection(songquery.collections![0])         mymusicplayer.play()     }      func countdown() {         timer--         // when countdown hits 0 should stop song.         if timer==0 {             mymusicplayer.stop()             clock.invalidate()             timer = 15         }      }  } 

this musiclibrary struct.

import foundation import mediaplayer  struct musiclibrary {     var musiclibrary: [songitem] = []      let query = mpmediaquery.songsquery()     var mediacollection : mpmediaitemcollection {         return mpmediaitemcollection(items: query.items!)     }      mutating func addsongs() {         index in 0..<mediacollection.count {             let mediaitem = mediacollection.items[index]             let songitem = songitem(                 title: mediaitem.title!,                 album: mediaitem.albumtitle!,                 artist: mediaitem.artist!,                 artwork: mediaitem.artwork!,                 persistentid: mediaitem.persistentid,                 genre: mediaitem.genre!             )              musiclibrary.append(songitem)         }     }      func getsong(index: int)->songitem {         return musiclibrary[index]     }      func getsongs()->[songitem] {         return musiclibrary     }  } 

and songitem struct

import foundation import mediaplayer  struct songitem {     var title: string     var album: string     var artist: string     var artwork: mpmediaitemartwork     var persistentid: uint64     var genre: string      init(title: string, album: string, artist: string, artwork: mpmediaitemartwork, persistentid: uint64, genre: string) {         self.title = title         self.album = album         self.artist = artist         self.artwork = artwork         self.persistentid = persistentid         self.genre = genre     }  }    

i change view controller along these lines:

import uikit import mediaplayer  class runningmusicviewcontroller: uiviewcontroller {     var index = 0     var timer: nstimer      let mymusic = musiclibrary()     let mymusicplayer = mpmusicplayercontroller()     let numsecondstoplay = 15.0     let songs = mymusic.getsongs()      @ibaction func startmusicbutton(sender: anyobject) {         playthesong(index: 0)         timer = nstimer.scheduledtimerwithtimeinterval(numsecondstoplay, target: self, selector: "playnextsong", userinfo: nil, repeats: true)     }       func playthesong(index: int) {         let songtoplay: songitem = songs[index]         print("song id=" + string(songtoplay.persistentid))         let predicate = mpmediapropertypredicate(value: int(songtoplay.persistentid), forproperty: mpmediaitempropertypersistentid)         let songquery = mpmediaquery()         songquery.addfilterpredicate(predicate)         mymusicplayer.setqueuewithitemcollection(songquery.collections![0])         mymusicplayer.play()     }      func playnextsong() {         mymusicplayer.stop()         if index < songs.count {             playthesong(index: index)             index += 1         }         else {             timer.invalidate()         }     } }