背景：在pushViewController之后把之前的vc删掉

先上代码

UIViewController *tempVC = [[UIViewController alloc] init];
[self.navigationController pushViewController:tempVC animated:YES];
NSMutableArray * subVCs = [NSMutableArray arrayWithArray:self.navigationController.viewControllers];
        for (int i=0; i<subVCs.count; i++) {
            if ([subVCs[i] isKindOfClass:[XXX class]]) {
                [subVCs removeObjectAtIndex:i];
            }
        }
        [self.navigationController setViewControllers:subVCs animated:YES];

大家一般都是这样做，可是，但是，pushViewController执行之后，有一定概率self.navigationController.viewControllers没有你刚才push的vc，这就是坑，它不是立马入栈的。

解决方法，很简单

• 设置代理
  self.navigationController.delegate = self;
• 实现代理函数

NSMutableArray * subVCs = [NSMutableArray arrayWithArray:self.navigationController.viewControllers];
        for (int i=0; i<subVCs.count; i++) {
            if ([subVCs[i] isKindOfClass:[XXX class]]) {
                [subVCs removeObjectAtIndex:i];
            }
        }
        [self.navigationController setViewControllers:subVCs animated:YES];

嗯，是不是很简单。