外类获取m文件变量

//获取

1. Ivar ivar = class_getInstanceVariable([VOLPlayManager class], "_info");
   InfoData * infoData = object_getIvar([VOLPlayManager getInstance], ivar);

2.  VLPKVOController *c = [self.avPlayer valueForKey:@"_playerItemKVO"];
    if (c!=NULL) {
        [c safelyAddObserver:self
                               forKeyPath:@"status"
                                  options:NSKeyValueObservingOptionInitial | NSKeyValueObservingOptionNew
                                  context:KVO_AVPlayerItem_state];
    }