Nested attributes text field isn't showing up in my views - ruby-on-rails-4

Question

I am new to the rails community. I am working on an application where users can have username with a nested attribute of first and last name. The other text field associated with the User model works fine.
Any help would be much appreciated.
Attached are the app models, controllers, migration files, db schema, and views.
models
class User < ActiveRecord::Base
has_one :username, dependent: :destroy
accepts_nested_attributes_for :username, allow_destroy: true
end
class Username < ActiveRecord::Base
belongs_to :user
end
Migrations
class CreateUsers < ActiveRecord::Migration
def change
create_table :users do |t|
t.string :email
t.string :about_me
t.string :nationality
t.string :sexe
t.timestamps null: false
end
end
end
class CreateUsernames < ActiveRecord::Migration
def change
create_table :usernames do |t|
add_column :username, :first_name, :string
add_column :username, :last_name, :string
t.references :user, index: true, foreign_key: true
t.timestamps null: false
end
end
end
controller
class UsersController < ApplicationController
def index
#all_users = User.all
#new_user = User.new
#username = Username.new
end
def new
#new_user = User.new
end
def create
User.create(user_params)
end
private
def user_params
params.require(:user).permit(:email, :about_me, username_attributes:
[:last_name, :first_name])
end
end
Views
<h1>Users#index</h1>
<p>Find me in app/views/users/index.html.erb</p>
<%= form_for #new_user do |f| %>
<%= f.fields_for #new_user do |user| %>
<div class="field">
<%= user.label :email%>
<%= user.text_field :email %>
<%= user.label :about_me %>
<%= user.text_field :about_me %>
</div>
<% end %>
<%= f.fields_for :username do |name| %>
<div class="field">
<%= name.label :first_name %>
<%= name.text_field :first_name %>
</div>
<% end %>
<div class="form-actions">
<%= f.button :submit %>
</div>
<% end %>

Answer 1

Try this
controller
def new
#new_user = User.new
#new_user.usernames.build
end
view
<%= form_for #new_user do |f| %>
# ...
<%= f.fields_for :usernames do |name| %>
<div class="field">
<%= name.label :first_name %>
<%= name.text_field :first_name %>
</div>
<% end %>
# ...
<% end %>
helper
def name_format(user_mst)
name = user_mst.first_name.capitalize
name += (" #{user_mst.last_name.capitalize}")
return name
end
to display on view