Storyboard Swift Generics

Storyboard+Loader.swift

//
//  Storyboard+Loader.swift
//  StoryboardGenerics
//
//  Created by Daniel Tavares on 29/04/2016.
//  Copyright © 2016 Daniel Tavares. All rights reserved.
//

import UIKit

protocol StoryboardLoader {}

extension StoryboardLoader where Self: RawRepresentable, Self.RawValue == String {
	func loadControllerInNavigationController<T: UIViewController>(controllerID: String) -> T? {
		return Loader.EmbeddedController(self.rawValue, identifier: controllerID).controller()
	}

	func loadController<T: UIViewController>() -> T? {
		return Loader.Name(self.rawValue).controller()
	}

	func loadController<T: UIViewController>(identifier identifier: String) -> T? {
		return Loader.Controller(self.rawValue, identifier: identifier).controller()
	}
}

extension UIStoryboard {
	func loadController<T: UIViewController>(type: T.Type) -> T? {
		guard let controller = self.instantiateViewControllerWithIdentifier(String(type)) as? T else {
			return nil
		}
		return controller
	}
}

private enum Loader<T: UIViewController> {
	case Name(String)
	case Controller(String, identifier: String)
	case EmbeddedController(String, identifier: String)
	func controller() -> T? {
		switch self {
		case let .Name(storyboard):
			let storyboard = UIStoryboard(name: storyboard, bundle: nil)
			guard let controller = storyboard.instantiateViewControllerWithIdentifier(String(T)) as? T else {
				return nil
			}
			return controller
		case let .Controller(storyboard, identifier):
			let storyboard = UIStoryboard(name: storyboard, bundle: nil)
			guard let controller = storyboard.instantiateViewControllerWithIdentifier(identifier) as? T else {
				return nil
			}
			return controller
		case let .EmbeddedController(storyboard, identifier):
			let storyboard = UIStoryboard(name: storyboard, bundle: nil)
			guard let navController = storyboard.instantiateViewControllerWithIdentifier(identifier) as? UINavigationController, controller = navController.viewControllers.first as? T else {
				return nil
			}
			return controller
		}
	}
}