Create nested hash RUBY

Question

i have an array of hashes, eg

array = [
{ id: 1, name: 'root' parent: null},
{ id: 2, name: 'first' parent: 1},
{ id: 5, name: 'first step' parent: 2},
{ id: 6, name: 'second step' parent: 2},

{ id: 3, name: 'second' parent: 1},
{ id: 7, name: 'first step' parent: 3},

{ id: 4, name: 'third' parent: 1},
{ id: 2, name: 'first' parent: 1},

]

and i need to build something like that

hash = {
  { 
  id: 1,
  name: 'root',
  parent: null,
  childrens: [
    { id: 2,
    name: 'first',
    parent: 1,
    childrens: [
      {
        id: 5,
        name: 'first step',
        parent: 2
      },
      {
        id: 6,
        name: 'second step',
        parent: 2
      },
  ]},
  ...
}

I am newbie at ruby and doesnot understand how to do this. Probably i need to use recursive functions? Or not?

Yes you will have to use a recursive function. ¿Is this something related to rails? — Jorge de los Santos
– Jorge de los Santos, Commented Jun 4, 2014 at 11:44
yes. In fact, i have awesome_nested_set and i need to make such thing with this gem — Sapotero
– Sapotero, Commented Jun 4, 2014 at 11:46
Never used this gem, but this other one worked perfect for me: github.com/stefankroes/ancestry ¿Is it an option? — Jorge de los Santos
– Jorge de los Santos, Commented Jun 4, 2014 at 11:51

Community · Accepted Answer · 2017-05-23 12:30:03Z

1

# Put all your nodes into a Hash keyed by id  This assumes your objects are already Hashes
object_hash = nodes.index_by {|node| node[:id]}
object_hash[0] = {:root => true}

# loop through each node, assigning them to their parents
object_hash.each_value {|node|
  next if node[:root]
  children = object_hash[node[:parent_id]][:children] ||= []
  children << node
}

#then your should have the structure you want and you can ignore 'object_hash' variable
tree = object_hash[0]

From the answer:

Algorithm for parsing a flat tree into a non-flat tree

edited May 23, 2017 at 12:30

CommunityBot

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answered Jun 4, 2014 at 11:56

Jorge de los Santos

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1 Comment

Sapotero Over a year ago

yes, its great, but we use awesome_nested_set and i cant use this gem

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