code: protected function getRecipeSlug() : ?RecipeSlug
      {
          if (!$this->recipeSlug && $this->recipeSlugString)
          {
              $this->recipeSlug = $this->recipeSlugRepository->findOneBySlug($this->recipeSlugString);
          }
  
          return $this->recipeSlug;
      }
docs: Optimalizace SQL
  @return RecipeSlug|NULL