How I display a list of child departments on my dashboard index

dashboard_controller.rb

class DashboardController < ApplicationController
  before_action :require_login
  before_filter :init
 
  def index
    @departments.each do |department|
      childfetch = Department.where(parent: "#{department.name}").select('name')
      instance_variable_set("@#{department.name}Children".gsub(' ','_'), childfetch.map { |child| "#{child.name}" }.join(',') )
    end
  end
  def office
 
  end
  def preferences
 
  end
  def company
  end
 
  private
 
  def require_login
    unless session[:user_id].present?
      redirect_to root_url
    end
  end
  def init
    @departments = Department.where(parent: '')
  end
end

dashboard_helper.rb

module DashboardHelper
	def instancevars(arg)
		instance_variable_get("@#{arg}Children".gsub(' ','_'))
	end
	def nameslug(arg)
		arg.downcase[0,5]
	end
end

index.html.erb

<ul class="accord-style">
	<% @departments.each do |department| %>
	<li <%= instancevars(department.name).present? ? "data-accord=#{nameslug(department.name)}":'' %>>
		<%= "#{department.name}" %>
	</li>
		<% if(instancevars(department.name).present?) %>
		<ul id="<%= nameslug(department.name) %>">
			<% instancevars(department.name).split(',').each do |child| %>
			<li><a href=""><%= "#{child}" %></a></li>
			<% end %>
		</ul>
		<% end %>
	<% end %>
</ul>