Adding Consistent Back Button to view

BaseController.swift

import UIKit

class BaseViewController: UIViewController {
    
    override func viewDidLoad() {
        
        super.viewDidLoad()
        
        let backTitle = NSLocalizedString("Back", comment: "Back button label")
        self.addBackbutton(backTitle)
        
    }
    
}

UIViewControllerExtension.swift

import UIKit

extension UIViewController {

    func backButtonAction() {
        self.dismissViewControllerAnimated(true, completion: nil)
    }
    
    func addBackbutton(title: String) {
        if let nav = self.navigationController,
            let item = nav.navigationBar.topItem {
            item.backBarButtonItem  = UIBarButtonItem(title: title, style: UIBarButtonItemStyle.Plain, target: self, action:
                #selector(self.backButtonAction))
        } else {
            if let nav = self.navigationController,
                let _ = nav.navigationBar.backItem {
                self.navigationController!.navigationBar.backItem!.title = title
            }
        }
    }
}