Geek Mama

Nested Sets and Scope

October 3rd, 2008

A colleague and I both had this same issue working with BNS and since there wasn’t much about it on the net, I figured I’d share.

Each TLD in my nested set will be its own tree root. And multiple tree roots in a nested set require a scope.


acts_as_nested_set :scope => :root


The ruby on rails wiki mentions scope using a root_id column, but you’ll notice in the example that the root records have a root_id of nil. This just doesn’t work.

When you attempt to move_to_child_of your new node record after create, you’ll recieve this error:

Impossible move, target node cannot be inside moved tree.

Now, we couldn’t find any documentation anywhere but after much trial and error my colleague discovered that populating the root_id of a root record with its own id, resolves the issue.


root = Domain.new
subdomains.each_with_index do |subdomain, index|
node = Domain.find_by_subdomain_and_parent_id(subdomain, parent.id)
if node.nil?
node = Domain.create(:subdomain => subdomain, root_id => root.id)
if parent.new_record? #is this a root record?
node.root_id = node.id # <-------------------------------- populate root for root records
node.save
root = node
else
node.move_to_child_of parent.id
end
end
parent = node
end


Entry Filed under: Ruby on Rails