After.swift

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    if recipes[indexPath.row].isPromoted {
      let promotedCell = tableView.dequeueReusableCell(withIdentifier: "promoted", for: indexPath) as! PromotedRecipeCell
      promotedCell.recipe = recipe
      promotedCell.promotion = recipe.promotion // we've guarded here using the isPromoted method, so the value is unwrapped
      return promotedCell
    } else {
      let normalCell = tableView.dequeueReusableCell(withIdentifier: "normal", for: indexPath) as! RecipeCell
      normalCell.recipe = recipe
      return normalCell
    }
}

extension Recipe {
 
  var isPromoted: Bool (guards promotion)
  
}