discourse/app/serializers/category_detailed_serializer.rb

class CategoryDetailedSerializer < ApplicationSerializer

  attributes :id,
             :name,
             :color,
             :text_color,
             :slug,
             :topic_count,
             :post_count,
             :topics_week,
             :topics_month,
             :topics_year,
             :description,
             :description_excerpt,
             :is_uncategorized

  has_many :featured_users, serializer: BasicUserSerializer
  has_many :displayable_topics, serializer: ListableTopicSerializer, embed: :objects, key: :topics

  def topics_week
    object.topics_week || 0
  end

  def topics_month
    object.topics_month || 0
  end

  def topics_year
    object.topics_year || 0
  end

  def is_uncategorized
    name == SiteSetting.uncategorized_name
  end

  def include_is_uncategorized?
    is_uncategorized
  end

  def include_displayable_topics?
    return displayable_topics.present?
  end

  def description_excerpt
    PrettyText.excerpt(description,300) if description
  end

end