iOS 返回前几个页面

 //从购物车或商品详情购买商品进入
        NSArray *pushVCAry=[self.navigationController viewControllers];
        //下面的pushVCAry.count-3 是让我回到视图1中去
        UIViewController *popVC=[pushVCAry objectAtIndex:pushVCAry.count-4];
        [self.navigationController popToViewController:popVC animated:YES];

 //得到当前视图控制器中的所有控制器
        NSMutableArray *array = [self.navigationController.viewControllers mutableCopy];
        //把B从里面删除
        if (_isForgetPassword) {
            [array removeObjectAtIndex:array.count - 3];
        }else {
            [array removeObjectAtIndex:array.count-2];

        }
        //把删除后的控制器数组再次赋值
        [self.navigationController setViewControllers:[array copy] animated:YES];