Module: DataMapper::Is::Tree::ClassMethods

Included Modules

DataMapper::Is::Tree::InstanceMethods

An extension to DataMapper to easily allow the creation of tree structures from your DataMapper models. This requires a foreign key property for your model, which by default would be called :parent_id. 

  Example:

  class Category
    include DataMapper::Resource
    include DataMapper::Is::Tree

    property :id, Integer
    property :parent_id, Integer
    property :name, String

    is_a_tree :order => "name"
  end

  root
    +- child
         +- grandchild1
         +- grandchild2

  root        = Category.create("name" => "root")
  child       = root.children.create("name" => "child")
  grandchild1 = child1.children.create("name" => "grandchild1")
  grandchild2 = child2.children.create("name" => "grandchild2")

  root.parent   # => nil
  child.parent  # => root
  root.children # => [child]
  root.children.first.children.first # => grandchild1
  Category.first_root  # => root
  Category.roots       # => [root]

The following instance methods are added:

  • children - Returns all nodes with the current node as their parent, in the order specified by :order ([grandchild1, grandchild2] when called on child)
  • parent - Returns the node referenced by the foreign key (:parent_id by default) (root when called on child)
  • siblings - Returns all the children of the parent, excluding the current node ([grandchild2] when called on grandchild1)
  • generation - Returns all the children of the parent, including the current node ( [grandchild1, grandchild2] when called on grandchild1)
  • ancestors - Returns all the ancestors of the current node ([root, child1] when called on grandchild2)
  • root - Returns the root of the current node (root when called on grandchild2)
Author:Timothy Bennett (http://lanaer.com)

Public Visibility

Public Instance Method Summary

#is_a_tree(options = {}) #can_has_tree

Configuration options are:.

Public Instance Methods Included from DataMapper::Is::Tree::InstanceMethods

ancestors, generation, root, siblings

Public Instance Method Details

is_a_tree

public is_a_tree(options = {})

Also known as: can_has_tree

Configuration options are:

  • child_key - specifies the column name to use for tracking of the tree (default: parent_id)
[View source] 


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# File 'dm-more/dm-is-tree/lib/dm-is-tree/is/tree.rb', line 61

def is_a_tree(options = {})
  configuration = { :child_key => :parent_id }
  configuration.update(options) if Hash === options

  many_to_one :parent, :class_name => name, :child_key => [ configuration[:child_key] ]
  has n, :children, :class_name => name, :child_key => [ configuration[:child_key] ]

  include DataMapper::Is::Tree::InstanceMethods

  class_eval "def self.roots\nall :\#{configuration[:child_key]} => nil, :order => \#{configuration[:order].inspect}\nend\n\ndef self.first_root\nfirst :\#{configuration[:child_key]} => nil, :order => \#{configuration[:order].inspect}\nend\n", __FILE__, __LINE__

  class << self





    alias_method :root, :first_root # for people used to the ActiveRecord acts_as_tree
  end
end