 - (void) removeSong: (NSString *)zSong{      //remove from reference playlist      NSSet *targets = [self lookUpTitle:zSong];      if ([targets count]>0) {         [self.masterSongs minusSet:targets];          for (Playlist *playlist in listOfPlaylists) {             // -all objects converts the set into array.              [playlist.songList removeObjectsInArray:[targets allObjects]];         }     }     else         ; }  