closure_tree | efficiently make your ActiveRecord models support | Dataset library

Note that closure_tree only supports ActiveRecord 4.2 and later, and has test coverage for MySQL, PostgreSQL, and SQLite. NOTE: Run rails g closure_tree:config to create an initializer with extra configurations. (Optional).
Add gem 'closure_tree' to your Gemfile
Run bundle install
Add has_closure_tree (or acts_as_tree, which is an alias of the same method) to your hierarchical model: class Tag < ActiveRecord::Base has_closure_tree end class AnotherTag < ActiveRecord::Base acts_as_tree end Make sure you check out the large number of options that has_closure_tree accepts. IMPORTANT: Make sure you add has_closure_tree after attr_accessible and self.table_name = lines in your model. If you're already using other hierarchical gems, like ancestry or acts_as_tree, please refer to the warning section!
Add a migration to add a parent_id column to the hierarchical model. You may want to also add a column for deterministic ordering of children, but that's optional. class AddParentIdToTag < ActiveRecord::Migration def change add_column :tags, :parent_id, :integer end end The column must be nullable. Root nodes have a NULL parent_id.
Run rails g closure_tree:migration tag (and replace tag with your model name) to create the closure tree table for your model. By default the table name will be the model's table name, followed by "_hierarchies". Note that by calling has_closure_tree, a "virtual model" (in this case, TagHierarchy) will be created dynamically. You don't need to create it.
Run rake db:migrate
If you're migrating from another system where your model already has a parent_id column, run Tag.rebuild! and your tag_hierarchies table will be truncated and rebuilt. If you're starting from scratch you don't need to call rebuild!.