custom attributes version of accepts_nested_attributes_for with reject_if

I am trying to create a custom version of this below

  accepts_nested_attributes_for :categories, :reject_if => proc { |hash| hash['title'].blank? }

So far what i got is

  def categories_attributes=(categories_attributes)
    categories_attributes.values.each do |category_attribute|
      category = Category.find_or_create_by(category_attribute)
      categories << category
    end
  end

But i am trying to add the reject_if part to it, i cant seem to figure it out. how can i replicate that portion into my custom attribute below?

Thanks!