How to register fonts in a Bundle without having to edit the plist

Bundle.RegisterFonts.swift

//
//  Bundle.swift
//  timerany
//
//  Created by Leo Dion on 12/2/16.
//  Copyright © 2016 BrightDigit. All rights reserved.
//

import Foundation
import CoreGraphics
import UIKit

public struct InvalidFontResource : Error {
  public let bundle : Bundle
  public let url : URL
}

public struct ErrorCollection : Error {
  public let errors: [Error]
}

public extension Bundle {
  public func registerFontResources(withExtensions extensions: [String]? = nil, inSubdirectory subdirectory: String? = nil) throws {
    let extensions = extensions ?? ["ttf", "otf"]
    let urls = extensions.flatMap({self.urls(forResourcesWithExtension: $0, subdirectory: subdirectory)}).flatMap({$0})
    
    let errors = urls.flatMap{
      (url) -> Error? in
      let data: Data
      let error: UnsafeMutablePointer<Unmanaged<CFError>?>? = nil
      do {
        data = try Data(contentsOf: url)
      } catch let error {
        return error
      }
      guard let provider = CGDataProvider(data: data as CFData) else {
        return InvalidFontResource(bundle: self, url : url)
      }
      let fontRef = CGFont(provider)
      if (!CTFontManagerRegisterGraphicsFont(fontRef, error)) {
        if let unmanagedError = error?.pointee {
          return unmanagedError.takeRetainedValue()
        } else {
          return NSError()
        }
      } else {
        return nil
      }
    }
    
    if errors.count > 0 {
      throw ErrorCollection(errors: errors)
    }
  }
}