Better UIStoryboard and UIViewController instantiation

UIStoryboardExtension.swift

//
//  UIStoryboardExtension.swift
//

import Foundation

/*

   This is an extension to help with UIStoryboard and UIViewController instantiation from identifier.
   The ultimate goal is to remove hard coded UIStoryboard and UIViewController identifiers in code.

   Usage: Your UIViewController must conform to StoryboardIdentifiable.

   When impact will be easier to mesure, we can conform all UIViewController to this protocol by an extension
   extension UIViewController: StoryboardIdentifiable { }

   But for now, we can provide this extension as a opt-in model instead.

   Storyboard identifier needs to match UIViewController class name.
   Implmentation example

   let storyboard = UIStoryboard.storyboard(.accountSettings)
   This will instantiate AccountSettings.storyboard from disk

   let profileViewController: ProfileViewController = storyboard.instantiateViewController()

   profileViewController is a ProfileViewController instance because storyboard identifier
   is ProfileViewController inside AccountSettings.storyboard.

 */

extension UIStoryboard {

    enum Storyboard: String {

        case accountSettings

        var filename: String {
            return rawValue.capitalized
        }
    }

    convenience init(storyboard: Storyboard, bundle: Bundle? = nil) {
        self.init(name: storyboard.filename, bundle: bundle)
    }

    func instantiateViewController<T: UIViewController>() -> T where T: StoryboardIdentifiable {
        if let viewController = self.instantiateViewController(withIdentifier: T.storyboardIdentifier) as? T {
            return viewController
        } else {
            fatalError("Couldn't instantiate view controller with identifier \(T.storyboardIdentifier) ")
        }
    }
}

protocol StoryboardIdentifiable {
    static var storyboardIdentifier: String { get }
}

extension StoryboardIdentifiable where Self: UIViewController {
    static var storyboardIdentifier: String {
        return String(describing: self)
    }
}