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equivalent/app-model-document.rb

Last active October 29, 2018 07:47
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Recursion example in Ruby on Rails model. Recursion will generate array of parents parents
Raw
app-model-document.rb
class Document < ActiveRecord::Base
belongs_to :parent, class_name: 'Document'
def self.get_ancestors(who)
@tree ||= []
# @tree is instance variable of Document class object not document instance object
# so: Document.get_instance_variable('@tree')
if who.parent.nil?
return @tree
else
@tree << who.parent
get_ancestors(who.parent)
end
end
def ancestors
@ancestors ||= Document.get_ancestors(self)
end
end
Raw
console
# Recursion will generate array of parents parents
d = Document.last
d.ancestors.collect(&:id)
# => [570, 569, 568]
Raw
db-migration-create_documents.rb
class CreateDocuments < ActiveRecord::Migration
def change
create_table :documents do |t|
t.integer :parent_id
t.string :file
t.timestamps
end
end
end
@samueladesoga
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For some reason i had some issue with the code you had written

this is what worked for me:

`def ancestors
ancestors = []
ancestors = Klass.get_ancestors(ancestors, self)
end

def self.get_ancestors(ancestor, klass)
if klass.parent.nil?
return ancestor
else
ancestor << klass.parent
Klass.get_ancestors(ancestor, klass.parent)
end
end`

@samueladesoga
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The issue i has was each time i created a new instance of the object, it remembered the previous ancestors

@douxsey
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douxsey commented Sep 4, 2018 •
edited
Loading

this worked for me

  def parents_id
    parents = []
    if parent
      parents << parent.id
      (parents << parent.parents).flatten
    else
      parents.flatten
    end
  end

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