未从iPhone音乐库播放选定音乐

// sample code that I have used in my application

self.player = [MPMusicPlayerController applicationMusicPlayer];
MPMediaPropertyPredicate *songNamePredicate = [MPMediaPropertyPredicate predicateWithValue: self.songName forProperty: MPMediaItemPropertyTitle];
MPMediaQuery *mySongQuery = [[MPMediaQuery alloc] init];
[mySongQuery addFilterPredicate: songNamePredicate];
[player setQueueWithQuery:mySongQuery];
[player play];

请帮我解决这个问题。