mathie

class NodesController < ActionController::Base
  def index
    @nodes = Node.roots.eager_load(:descendants)
  end
end

mathie

<li>
  <%= link_to node.name, node %>

  <% if node.children.present? %>
    <ul>
      <%= render node.children %>
    </ul>
  <% end %>
</li>

mathie

<ul>
  <%= render @nodes %>
</ul>

mathie

class NodesController < ActionController::Base
  def index
    @nodes = Node.roots
  end
end

mathie

class Node < ActiveRecord::Base
  def descendants
    self.class.where(“:id = ANY(path)”, id: id)
  end
end

mathie

class Node < ActiveRecord::Base
  def children
    self.class.where(path: path + [id])
  end
end

mathie

class Node < ActiveRecord::Base
  def siblings
    self.class.where(path: path)
  end
end

mathie

class Node < ActiveRecord::Base
  def ancestors
    if path.present?
      self.class.where(id: path)
    else
      self.class.none
    end
  end
end

mathie

class Node < ActiveRecord::Base
  def parent
    if parent_id = path.last
      self.class.find(parent_id)
    else
      nil
    end
  end
end

mathie

class Node < ActiveRecord::Base
  def root
    if root_id = path.first
      self.class.find(root_id)
    else
      self
    end
  end
end