Tag, TagCategory & Tagging

The taxonomy models, installed by the taxonomies generator. Make any model taggable with the Taggable concern.

Tag

Column	Type	Notes
key	string	required, unique within its category, or among the tags without one
name	string	required display name
category_id	bigint	optional TagCategory
position	integer	ordering within the category
taggings_count	integer	counter cache

• belongs_to :category, has_many :taggings, and taggables, the tagged records of any model
• Scopes: ordered, in_category(key), in_categories(keys)

Two categories may share a key: a Colors category and a Fruits category can both have an orange tag. The model validates the rule, and the database holds it too, with a unique index on category_id and key, plus one on key for the tags without a category (in a unique index, NULLs never collide).

TagCategory

Column	Type	Notes
key	string	required, unique
name	string	required display name
position	integer	ordering
tags_count	integer	counter cache

• has_many :tags (ordered). A category can't be deleted while it has tags: left without a category, their keys could collide with others'. Move or delete them first; the admin says so.
• Scopes: ordered, with_tags

Tagging

The polymorphic join between a Tag and any taggable record, unique per (taggable, tag) pair, with counter caches on both sides.

class Article < ApplicationRecord
  include Trek::Taggable
end

article.tags << Tag.in_category("topics").first
article.tag_names # => ["Ruby"]