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module ActiveRecord
module Mixins
# Including this mixin if you want to model a tree structure by providing a parent association and an children
# association. This mixin assumes that you have a column called parent_id
#
# class Category < ActiveRecord::Base
# include ActiveRecord::Mixins::Tree
# end
#
# Example :
# root
# \_ child1
# \_ sub-child1
#
# 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
module Tree
def self.append_features(base)
super
base.module_eval <<-associations
belongs_to :parent, :class_name => name, :foreign_key => "parent_id"
has_many :children, :class_name => name, :foreign_key => "parent_id", :order => "id", :dependent => true
associations
end
end
end
end
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