module ActsAsTree::ClassMethods
Specify this acts_as
extension if you want to model a tree structure by providing a parent association and a children association. This requires that you have a foreign key column, which by default is called parent_id
.
class Category < ActiveRecord::Base include ActsAsTree acts_as_tree :order => "name" end Example: root \_ child1 \_ subchild1 \_ subchild2 root = Category.create("name" => "root") child1 = root.children.create("name" => "child1") subchild1 = child1.children.create("name" => "subchild1") root.parent # => nil child1.parent # => root root.children # => [child1] root.children.first.children.first # => subchild1
In addition to the parent and children associations, the following instance methods are added to the class after calling acts_as_tree
:
-
siblings
- Returns all the children of the parent, excludingthe current node (<tt>[subchild2]</tt> when called on <tt>subchild1</tt>)
-
self_and_siblings
- Returns all the children of the parent,including the current node (<tt>[subchild1, subchild2]</tt> when called on <tt>subchild1</tt>)
-
ancestors
- Returns all the ancestors of the current node(<tt>[child1, root]</tt> when called on <tt>subchild2</tt>)
-
root
- Returns the root of the current node (root
when called on <tt>subchild2</tt>)
Public Class Methods
Returns a hash of all nodes grouped by their level in the tree structure.
Class.generations # => { 0=> [root1, root2], 1=> [root1child1, root1child2, root2child1, root2child2] }
# File lib/acts_as_tree.rb, line 131 def self.generations all.group_by{ |node| node.tree_level } end
Public Instance Methods
Configuration options are:
-
primary_key
- specifies the column name for relations(default: +id+)
-
foreign_key
- specifies the column name to use for trackingof the tree (default: +parent_id+)
-
order
- makes it possible to sort the children according tothis SQL snippet.
-
counter_cache
- keeps a count in achildren_count
columnif set to +true+ (default: +false+). Specify a custom column by passing a symbol or string.
# File lib/acts_as_tree.rb, line 66 def acts_as_tree(options = {}) configuration = { primary_key: "id", foreign_key: "parent_id", order: nil, counter_cache: nil, dependent: :destroy, touch: false } configuration.update(options) if options.is_a?(Hash) if configuration[:counter_cache] == true configuration[:counter_cache] = :children_count end belongs_to_opts = { class_name: name, primary_key: configuration[:primary_key], foreign_key: configuration[:foreign_key], counter_cache: configuration[:counter_cache], touch: configuration[:touch], inverse_of: :children } belongs_to_opts[:optional] = true if ActiveRecord::VERSION::MAJOR >= 5 belongs_to :parent, belongs_to_opts if ActiveRecord::VERSION::MAJOR >= 4 has_many :children, lambda { order configuration[:order] }, class_name: name, primary_key: configuration[:primary_key], foreign_key: configuration[:foreign_key], dependent: configuration[:dependent], inverse_of: :parent else has_many :children, class_name: name, primary_key: configuration[:primary_key], foreign_key: configuration[:foreign_key], order: configuration[:order], dependent: configuration[:dependent], inverse_of: :parent end class_eval <<-EOV include ActsAsTree::InstanceMethods def self.default_tree_order order_option = #{configuration[:order].inspect} order(order_option) end def self.root self.roots.first end def self.roots where(:#{configuration[:foreign_key]} => nil).default_tree_order end EOV # Returns a hash of all nodes grouped by their level in the tree structure. # # Class.generations # => { 0=> [root1, root2], 1=> [root1child1, root1child2, root2child1, root2child2] } def self.generations all.group_by{ |node| node.tree_level } end if configuration[:counter_cache] after_update :update_parents_counter_cache def children_counter_cache_column reflect_on_association(:parent).counter_cache_column end def leaves where(children_counter_cache_column => 0).default_tree_order end else # Fallback to less efficient ways to find leaves. class_eval <<-EOV def self.leaves internal_ids = select(:#{configuration[:foreign_key]}).where(arel_table[:#{configuration[:foreign_key]}].not_eq(nil)) where("\#{connection.quote_column_name('#{configuration[:primary_key]}')} NOT IN (\#{internal_ids.to_sql})").default_tree_order end EOV end end
# File lib/acts_as_tree.rb, line 139 def children_counter_cache_column reflect_on_association(:parent).counter_cache_column end
# File lib/acts_as_tree.rb, line 143 def leaves where(children_counter_cache_column => 0).default_tree_order end