Cocoon Gem not displaying form - rails 4 - ruby-on-rails

Question

I am unsure why my cocoon nested form is not appearing and any help would be much appreciated
the <button><%= link_to_add_association 'add a required skill', f, :requiredskills %></button> works perfectly well in displaying a form
but i am unsure why this is not rendering the form <%= render 'requiredskill_fields', :f => duty %>
what i would like to do is to have a form already displayed and when a user clicks add a required skill another form is displayed.
At present when a user clicks add a required skill that displays
another form - the main issue is having a form to be displayed
initially. I am assuming this <%= render 'requiredskill_fields', :f
=> duty %> is suppose to put a form in place but i am unsure why it is not working
user/_form.html.erb
<%= simple_form_for(#user) do |f| %>
<%= f.error_notification %>
<div class="form-inputs">
<%= f.input :firstname %>
<%= f.input :lastname %>
<h3>required skills & expertise</h3>
<div>
<div class="requiredskill_info" id="skill">
<%= f.simple_fields_for :requiredskills do |skill| %>
<%= render 'requiredskill_fields', :f => skill %>
<% end %>
<div class="add_requiredskill"><button><%= link_to_add_association 'add a required skill', f, :requiredskills %></button></div>
</div>
</div>
</div>
<div class="form-actions">
<%= f.button :submit %>
</div>
<% end %>
user/_requiredskill_fields.html.erb
<div class="nested-fields">
<%= f.association :category_advert, collection: CategoryAdvert.all, prompt: "select a category" %>
<%= f.grouped_collection_select :category_advertskill_id, CategoryAdvert.order(:name), :category_advertskills, :name, :id, :name, {prompt: "Select a category"}, {class: "category_advertskill"} %>
<button><%= link_to_remove_association 'remove required skill', f %></button>
</div>
users_controller.rb
class UsersController < ApplicationController
respond_to :html, :xml, :json
before_action :set_user, only: [:show, :edit, :update, :destroy]
def index
#users = User.all
#user = current_user
end
def show
#resume = #user.resume
end
def edit
end
def update
#user.update(user_params)
redirect_to #user
end
private
def set_user
#user = User.find(params[:id])
end
def user_params
params.require(:user).permit(:email, :firstname, :lastname, :city, :category_qualification_id, :category_careerlevel_id, :desiredjob, :category_distance_id, :preferedlocation, :category_notice_id, :category_country_id, :category_positiontype_id, :image, :cvattachment, :hidecv, :jobadvice, :validlicense, :owntransport, :considerrelocation, :preferredlocation, :neednotice, :stratdate, :availabletowork, :category_outsource_id, :category_advertskill_id, :category_age_id, languages_attributes: [:id, :name, :_destroy], requiredskills_attributes: [:id, :name, :category_advert_id, :category_advertskill_id, :category_year_id, :category_level_id, :_destroy])
end
end
user.rb
class User < ActiveRecord::Base
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
has_many :requiredskills
has_many :category_advertskills, through: :requiredskills
has_many :category_adverts, through: :requiredskills
has_one :resume
accepts_nested_attributes_for :languages, :reject_if => :all_blank, :allow_destroy => true
accepts_nested_attributes_for :requiredskills, :reject_if => :all_blank, :allow_destroy => true
end

Answer 1

def edit
#requiredskills = #user.requiredskills.present? ? #user.requiredskills : #user.requiredskills.build
end
change this code in controller