• 页面消失的时候

- (void)viewWillDisappear:(BOOL)animated {
    NSArray *viewControllers = self.navigationController.viewControllers;//获取当前的视图控制其
    if (viewControllers.count > 1 && [viewControllers objectAtIndex:viewControllers.count-2] == self) {
        //当前视图控制器在栈中，故为push操作
        NSLog(@"push");
    } else if ([viewControllers indexOfObject:self] == NSNotFound) {
        //当前视图控制器不在栈中，故为pop操作
        NSLog(@"pop");
    }
}