How do you use MPMediaItemPropertyPersistentID to play music in iPhone Music Player Framework? - ios4

Question

My code sucessfully catalogs song names and ID's for my the entire music library. However, it will not actually play a song using this methodology and the console displays the following:
Message playbackState timed out.
Message nowPlayingItem timed out.
self.musicPlayer = [MPMusicPlayerController applicationMusicPlayer];
MPMediaQuery *everything = [[MPMediaQuery alloc] init];
NSArray *itemsFromGenericQuery = [everything items];
SongName = [[NSMutableArray alloc] init];
SongItem = [[NSMutableArray alloc] init];
NSString *songTitle;
NSString *songID;
//Collect names & ID for entire music library & put into arrays
for (MPMediaItem *song in itemsFromGenericQuery) {
songTitle = [song valueForProperty: MPMediaItemPropertyTitle];
[SongName addObject:songTitle];
songID = [song valueForProperty: MPMediaItemPropertyPersistentID];
[SongItem addObject:songID];
}
NSLog (#"%#", [SongName objectAtIndex:1]);
NSLog (#"%#", [SongItem objectAtIndex:1]);
// Play the second song in the list
MPMediaItemCollection *collection = [MPMediaItemCollection collectionWithItems:[NSArray arrayWithObject:[SongItem objectAtIndex:1]]];
[self.musicPlayer setQueueWithItemCollection:collection];
[self.musicPlayer play];

Answer 1

Once again, I'll answer my own question. The issue was that collectionWithItems: expects an array of MPMediaItems, not an array of MPMediaItemPropertyPersistentIDs. Here is the working code for anyone who may have the same problem:
MPMediaQuery *everything = [[MPMediaQuery alloc] init];
NSArray *itemsFromGenericQuery = [everything items];
SongItem = [[NSMutableArray alloc] init];
for (MPMediaItem *song in itemsFromGenericQuery) {
NSString *songTitle = [song valueForProperty: MPMediaItemPropertyTitle];
//NSLog (#”%#”, songTitle);
songID = [song valueForProperty: MPMediaItemPropertyPersistentID];
//NSLog (#”%#”, songID);
[SongItem addObject:songID];
}
//Choose the first indexed song
NSString *selectedTitle = [SongItem objectAtIndex:0];
//Use the MPMediaItemPropertyPersistentID to play the song
MPMediaPropertyPredicate *predicate = [MPMediaPropertyPredicate predicateWithValue:selectedTitle forProperty:MPMediaItemPropertyPersistentID];
MPMediaQuery *mySongQuery = [[MPMediaQuery alloc] init];
[mySongQuery addFilterPredicate: predicate];
[musicPlayer setQueueWithQuery:mySongQuery];
[musicPlayer play];