When I Used [UITabBarController setSelectedIndex:] and - popToRootViewControllerAnimated:, the viewController not dealloc

Question

When I Used [UITabBarController setSelectedIndex:] and - popToRootViewControllerAnimated:, for example:

- (void)backViewControllerAnimation:(BOOL)animation {
    if ([self.navigationController respondsToSelector:@selector(interactivePopGestureRecognizer)]) {
        self.navigationController.interactivePopGestureRecognizer.enabled = YES;
    }

    [OLTabBarController.defaultTabBar.tabBarController setSelectedIndex:0];
    [self.navigationController popToRootViewControllerAnimated:YES];
}

the viewController is not dealloc, but if I delete [UITabBarController setSelectedIndex:0], like this:

- (void)backViewControllerAnimation:(BOOL)animation {
    if ([self.navigationController respondsToSelector:@selector(interactivePopGestureRecognizer)]) {
        self.navigationController.interactivePopGestureRecognizer.enabled = YES;
    }

    [self.navigationController popToRootViewControllerAnimated:YES];
}

the viewController can dealloc, I want known what happend, I need - setSelectedIndex: method, how can I make viewController perform - dealloc method?