Question

here is a piece of my code, but in this way, when I push the third level view controller, the tabbar won’t show.

//at first level
SecondLevelViewController *_2vc = [[SecondLevelViewController alloc]initWithNibName:@"SecondLevelViewController" bundle:nil];
    _2vc.hidesBottomBarWhenPushed = YES;
    [self.navigationController pushViewController:_2vc animated:YES];  

//at second level
ThirdLevelViewController *_3vc = [[ThirdLevelViewController alloc]initWithNibName:@"ThirdLevelViewController" bundle:nil];
    _3vc.hidesBottomBarWhenPushed = NO;
    [self.navigationController pushViewController:_3vc animated:YES];

Answer 1

Instead of setting the values of hidesBottomBarWhenPushed when you initialise the view controllers, you should instead handle the hiding mechanism in the -(void)viewWillAppear:(BOOL)animated in the view controllers instead.

An example of this implementation would be:

In SecondLevelViewController.m

-(void)viewWillAppear:(BOOL)animated
{
   [_bottomBar setHidden:YES];
}

In ThirdLevelViewController.m

-(void)viewWillAppear:(BOOL)animated
{
   [_bottomBar setHidden:NO];
}