CameraViewController.swift

import UIKit

class CameraViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    @IBAction func dismiss() {
        dismiss(animated: true)
    }
}

TabBarController.swift

import UIKit

class TabBarController: UITabBarController, UITabBarControllerDelegate {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        self.delegate = self
    }
    
    func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {
        if let identifier = viewController.restorationIdentifier, identifier == "cameraVC" {
            let vc = self.storyboard?.instantiateViewController(withIdentifier: "cameraVC") as! CameraViewController
            present(vc, animated: true, completion: nil)
            return false
        }
        
        return true
    }
}