What's wrong with association with user and emergency contact? - ruby-on-rails

Question

I am working on authentication part. Also, I am new to rails view part.
Here, I am trying to signup with required field but I am getting error message which is due to association between user and emergency contact. Can anyone suggest how to resolve it? Thanks in advance.
user.rb
class User < ApplicationRecord
has_one :emergency_contact, foreign_key: 'user_id'
end
emergency_contact.rb
class EmergencyContact < ApplicationRecord
belongs_to :user
end
registrations/new.html.erb
<h2>Sign up form</h2>
<%= form_for(resource, as: resource_name, url: registration_path(resource_name)) do |f| %>
<div class="field">
<%= f.label :email %><br />
<%= f.email_field :email, autofocus: true, autocomplete: "email" %>
</div>
<div class="field">
<%= f.label :password %>
<% if #minimum_password_length %>
<em>(<%= #minimum_password_length %> characters minimum)</em>
<% end %><br />
<%= f.password_field :password, autocomplete: "new-password" %>
</div>
<h3>Emergency Contact</h3>
<div>
<%= f.fields_for :emergency_contact, EmergencyContact.new do |emergency_contact| %>
<div>
<%= emergency_contact.label :full_name %> <br />
<%= emergency_contact.text_field :er_full_name %> <br />
</div>
<% end %>
</div>
<div class="actions">
<%= f.submit "Sign up" %>
</div>
<% end %>
<%= render "devise/shared/links" %>
users_controller.rb
class UsersController < ApplicationController
before_action :set_user, only: [:show, :edit, :update, :destroy]
def index
#users = User.all
end
def show
end
def new
#user = User.new
end
def edit
end
def create
#user = User.new(user_params)
respond_to do |format|
if #user.save
format.html { redirect_to #user, notice: 'User was successfully created.' }
format.json { render :show, status: :created, location: #user }
else
format.html { render :new }
format.json { render json: #user.errors, status: :unprocessable_entity }
end
end
end
def update
respond_to do |format|
if #user.update(user_params)
format.html { redirect_to #user, notice: 'User was successfully updated.' }
format.json { render :show, status: :ok, location: #user }
else
format.html { render :edit }
format.json { render json: #user.errors, status: :unprocessable_entity }
end
end
end
def destroy
#user.destroy
respond_to do |format|
format.html { redirect_to users_url, notice: 'User was successfully destroyed.' }
format.json { head :no_content }
end
end
private
def set_user
#user = User.find(params[:id])
end
def user_params
params.require(:user).permit(:email, :password,emergency_contact_attributes: [:er_full_name] )
end
end
Error message:
1 error prohibited this user from being saved:
Emergency contact user must exist

Answer 1

controller:
def new
#user = User.new
#emergency_contact = #user.build_emergency_contact
end
view:
<%= form.fields_for #emergency_contact do |emergency_contact_fields| %>
<div>
<%= emergency_contact_fields.label :full_name %> <br />
<%= emergency_contact_fields.text_field :er_full_name %> <br />
</div>
<% end %>