Recursion in Ruby. How to implement?

Question

ruby

Let's say there is a model of departments with a "master - child" relationship:

District
id
id_parent

How can I iterate over all id-shniki starting from the main to the last child?
Do not offer gems!!!

Answer 1

Monsieur wishes strange))

def walk_tree(root_id)
  root_item = Distinct.find(root_id)
  items = Distinct.where(parent_id: root_item.id)
  items.each { |item| walk_tree(item.id) }
end

If the model is in the database, then there will be a bunch of requests, you can get rid of this by immediately reading all the entries in the hash and searching for it