UIModalPresentationStyle.CurrentContext Swift iOS 7

Question

I want to show a View - PresentedView over another view - Background View using iOS 7. In my app, I am using UITabBArController, so at runtime I don't know which view would be the background view (could be any of the tab bar items). Below is the structure:

UITabBarController
  ---> TabItem1 - FirstUIViewController
  ---> TabItem2 - SecondUIViewController
  ---> TabItem3 - ThirdUIViewController

Need something Like this:

When app loads, I am on TabItem1 - FirstUIViewController. When I click on TabItem3, I want ThirdUIViewController to appear on Top on FirstUIViewController and 'FirstUIViewController' should appear in background with no user interaction enabled.

What I did so far:

1. Since, UIViewControllers are added as Relationship Controllers to appear as TabBar Item in `UITabBarController, I added a segue from tabbarcontroller to ThridViewController.

2. Changed PresentationStyle for this Segue to UIModalPresentationStyle.CurrentContext and did below modification

   func `viewDidLoad()` {
       super.viewDidLoad()
       self.performSegue("identifier", sender: self)
   }
   

Nothing happens and I just see 'ThridViewController' with white background

3. I tried manual coding approach:

   func `viewDidLoad()` {
       super.viewDidLoad()
       let overlayController:UIThirdViewController = UIThirdViewController() //This controller has a view added on top of it, which covers top half screen only
       overlayController.modalPresentationStyle = UIModalPresentationStyle.CurrentContext
       self.presentViewController(overlayController, animated: true, completion: nil)
   }
   

No change. New view overrides the previos view. if I add this overlayController.view.backgroundColor = UIColor.clearColor(), I see half screen black and half containing my new view

Problem Points:

1. Where should I write the code to initialize/call ThirdViewController to appear on top of current view?
2. How to fix the black screen issue and make it work on iOS 7?

I am using Xcode 7 and running on iOS7. Please help. Working code snippet will be appreciated. Don't post other stack overflow posts as answer, unless code works & you have tried on your own.

UPDATE: - With this approach, I get a black screen

class TabBarViewController: UITabBarController, UITabBarControllerDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()
        self.delegate = self
    }

    func tabBarController(tabBarController: UITabBarController, shouldSelectViewController viewController: UIViewController) -> Bool {

        let switchController:UIViewController = SwitchViewController()

        self.presentingViewController?.modalPresentationStyle = UIModalPresentationStyle.CurrentContext
        self.presentingViewController?.view.backgroundColor = UIColor.clearColor()
        self.presentViewController(switchController, animated: true, completion: nil)
        return false
    }
}

Answer 1

Make it a Custom Container View Controller (Apple Docs). Working example code:

class MyTabVC: UITabBarController, UITabBarControllerDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()
        self.delegate = self
    }

    func tabBarController(tabBarController: UITabBarController, shouldSelectViewController viewController: UIViewController) -> Bool {
        presentThirdVC()
        return false
    }

    func presentThirdVC() {
        let myThirdVC = MyThirdVC.makeVC()

        myThirdVC.view.backgroundColor = UIColor.blackColor().colorWithAlphaComponent(0.1)
        addChildViewController(myThirdVC)
        var newFrame = CGRectInset(view.bounds, 0, 50) // hack, do what you want
        myThirdVC.view.frame = newFrame
        view.addSubview(myThirdVC.view)
        didMoveToParentViewController(myThirdVC)
    }

}

class MyThirdVC: UIViewController {
    class func makeVC() -> MyThirdVC {
        return UIStoryboard(name: "Main", bundle: nil).instantiateViewControllerWithIdentifier("myThirdVC") as! MyThirdVC
    }
}

Screenshot: