new.html.erb

<h2>Sign up</h2>

<!--<% resource.profile || resource.build_profile %> -->
<% resource.build_profile %>
<%= form_for(resource, as: resource_name, url: registration_path(resource_name)) do |f| %>
  <%= devise_error_messages! %>

  <div class="field">
    <%= f.label :email %><br />
    <%= f.email_field :email, autofocus: true %>
  </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: "off" %>
  </div>

  <div class="field">
    <%= f.label :password_confirmation %><br />
    <%= f.password_field :password_confirmation, autocomplete: "off" %>
  </div>

<!-- For User profile registration-->
  <div class="field">
    <%= f.fields_for :profile do |profile_form| %>
    <p><%= profile_form.label :first_name %></p>
    <p><%= profile_form.text_field :first_name %></p>
    </div>

  
    <p><%= profile_form.label :last_name %></p>
    <p><%= profile_form.text_field :last_name %></p>


  
    <p><%= profile_form.label :username %></p>
    <p><%= profile_form.text_field :username %></p>
  

  
    <p><%= profile_form.label :email %></p>
    <p><%= profile_form.text_field :email %></p>


  
    <p><%= profile_form.label :phone %></p>
    <p><%= profile_form.text_field :phone %></p>
  

  
    <p><%= profile_form.label :delivery_address %></p>
    <p><%= profile_form.text_area :delivery_address %></p>
 
  <% end %>
 

  <div class="actions">
    <%= f.submit "Sign up" %>
  </div>
<% end %>

<%= render "users/shared/links" %>

registrationcontroller.rb

 def sign_up_params
    devise_parameter_sanitizer.sanitize(:sign_up)
    params.require(:user).permit(:email, :password, profile_attributes: [:first_name, :last_name, :username, :email, :phone, :delivery_address])
  end

user.rb

devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

         has_one :profile

         accepts_nested_attributes_for :profile