1、在融云的demo中看到这样一句代码,自动判断是用pop,还是dismiss退出当前视图
NSArray *viewControllers = self.navigationController.viewControllers;//获取当前的视图控制器
if ([viewControllers indexOfObject:self] == NSNotFound) {
//当前视图控制器不在栈中,故为pop操作
[self.realTimeLocation removeRealTimeLocationObserver:self];
self.realTimeLocation = nil;
}