how to display half modalView just above the tabBarController?

Question

I'm using tabBarController and navigationController I'm displaying a Half ModalView as child over one of the viewControllers of the TabBarController. Note I'm using iPhone-5 simulator. My problem is that the topViewController height is 504 even though it should be 568 I can't determine the right position to display it just above the tabBar.

UIViewController *viewCon =  [(UINavigationController*)[tabBarController selectedViewController] topViewController];

     UIViewController*vc=[tabBarController.viewControllers objectAtIndex:0];
        NSLog(@"vc,%f",vc.view.frame.size.height);// prints 568

        if (viewCon.childViewControllers.count == 0) {

        UIStoryboard* story = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
        _modal = [story instantiateViewControllerWithIdentifier:@"HalfModal"];
        [viewCon addChildViewController:_modal];

        _modal.view.frame = CGRectMake(0, screenHeight ,screenWidth, screenHeight);

        NSLog(@"TopviewController height ,%f",CGRectGetHeight(viewCon.view.frame));//prints 504

        frame = CGRectMake(0, 0, screenWidth, screenHeight);
        _view2 = [[UIView alloc]initWithFrame:frame];

        [viewCon.view addSubview:_view2];
        [viewCon.view addSubview:_modal.view];

        [UIView animateWithDuration:0.5
                         animations:^{
                             [_view2 setBackgroundColor:[UIColor colorWithWhite:0 alpha:0.5]];                             

                             _modal.view.frame = CGRectMake(0, screenHeight/2, 320, 284);

                         }
                         completion:^(BOOL finished) {
                             [_modal didMoveToParentViewController:viewCon];
                         }];

Answer 1

First of all I would recommend to avoid things like this

CGRectMake(0, screenHeight/2, 320, 284);

(constants for settings sizes/positions of elements), you must calculate it from UIScreen object.

CGFloat screenWidth = [UIScreen mainScreen].bounds.size.width

And second: if you want to display top most view you can try to add it to UIWindow