I want to add the option for the user to edit his email/password/image... from the /settings page not from the /users/edit page. So I copied the code to the settings page
    <%= form_for(resource, as: resource_name, url: registration_path(resource_name), html: { method: :put }) do |f| %>
  <%= devise_error_messages! %>
  <div class="field">
    <%= f.label :email %><br />
    <%= f.email_field :email, autofocus: true %>
  </div>
  <% if devise_mapping.confirmable? && resource.pending_reconfirmation? %>
    <div>Currently waiting confirmation for: <%= resource.unconfirmed_email %></div>
  <% end %>
  <div class="form-group">
    <%= f.label :image %>
    <%= f.file_field :image, class: 'form-control'%>
  </div>
  <div class="form-group">
    <%= f.label :cover %>
    <%= f.file_field :cover, class: 'form-control'%>
  </div>
  <div class="field">
    <%= f.label :password %> <i>(leave blank if you don't want to change it)</i><br />
    <%= f.password_field :password, autocomplete: "off" %>
  </div>
  <div class="field">
    <%= f.label :password_confirmation %><br />
    <%= f.password_field :password_confirmation, autocomplete: "off" %>
  </div>
  <div class="field">
    <%= f.label :current_password %> <i>(we need your current password to confirm your changes)</i><br />
    <%= f.password_field :current_password, autocomplete: "off" %>
  </div>
  <div class="actions">
    <%= f.submit "Update" %>
  </div>
<% end %>
<h3>Cancel my account</h3>
<p>Unhappy? <%= button_to "Cancel my account", registration_path(resource_name), data: { confirm: "Are you sure?" }, method: :delete %></p>
<%= link_to "Back", :back %>
but it returned this
undefined local variable or method `resource' for #<#<Class:0x007f60245ab9b0>:0x007f6026f58358>
What should I add to my controller?