为了回答你的第一个问题，你可以使用Notification作为

For answer to your first question, You can use Notification for the same as

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(songFinished:)
                                             name:AVPlayerItemDidPlayToEndTimeNotification
                                           object:[yourAVPlayer currentItem]];

-(void)songFinished:(NSNotification *)notification
{
     //Do your next stuff here;
}