注册时未定义的方法错误

Question

我有一张桌子＆＃39;用户＆＃39;各种专栏。其中一列是用户名。我决定通过迁移删除该列。在这样做之后，我尝试通过注册表单创建一个新用户（创建操作）但是我收到了用户名的未定义方法错误，我不知道为什么。错误被@ user.save抛出。

以下是相关代码，首先是用户控制器的操作，然后是提交的实际表单。

def user_params
  params.require(:user).permit(:name, :email, :password, :password_confirmation)
end

def create
  @user = User.new(user_params)
  if @user.save
    session[:user_id] = @user.id
    redirect_to @user, notice: 'Thank you for registering!'
  else
    render :new 
  end
end

<%= form_for(@user) do |f| %>
  <%= render "shared/errors", object: @user %>
  <fieldset>
    <ol>
      <li class="required">
        <%= f.label :name %>
        <%= f.text_field :name, size: 40, autofocus: true %>
      </li>
      <li class="required">
        <%= f.label :email %>
        <%= f.email_field :email, size: 40 %>
      </li>
      <li class="required">
        <%= f.label :password %>
        <%= f.password_field :password, size: 40 %>
      </li>
      <li class="required">
        <%= f.label :password_confirmation, "Confirm Password" %>
        <%= f.password_field :password_confirmation, size: 40 %>
      </li>
    </ol>
    <p>
      <% if @user.new_record? %>
        <%= f.submit "Create Account" %>
      <% else %>
        <%= f.submit "Update Account" %>
      <% end %>
    </p>
  </fieldset>
<% end %>

有什么想法？堆栈跟踪，按要求：

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activesupport（4.0.5）lib / active_support / callbacks.rb:80:in run_callbacks' activemodel (4.0.5) lib/active_model/validations/callbacks.rb:106:in run_validations！＆＃39; activemodel（4.0.5）lib / active_model / validations.rb：314：valid?' activerecord (4.0.5) lib/active_record/validations.rb:70:in有效吗？＆＃39; activerecord（4.0.5）lib / active_record / validations.rb:77:in perform_validations' activerecord (4.0.5) lib/active_record/validations.rb:51:in save＆＃39; activerecord（4.0.5）lib / active_record / attribute_methods / dirty.rb：32：在save' activerecord (4.0.5) lib/active_record/transactions.rb:270:in块（2级）中保存＆＃39; activerecord（4.0.5）lib / active_record / transactions.rb：330：在事务中的block in with_transaction_returning_status' activerecord (4.0.5) lib/active_record/connection_adapters/abstract/database_statements.rb:213:in块中＆＃39; activerecord（4.0.5）lib / active_record / connection_adapters / abstract / database_statements.rb:221:in within_new_transaction' activerecord (4.0.5) lib/active_record/connection_adapters/abstract/database_statements.rb:213:in transaction＆＃39; activerecord（4.0.5）lib / active_record / transactions.rb：209：在transaction' activerecord (4.0.5) lib/active_record/transactions.rb:327:in with_transaction_returning_status＆＃39; activerecord（4.0.5）lib / active_record / transactions.rb：270：in block in save' activerecord (4.0.5) lib/active_record/transactions.rb:285:in rollback_active_record_state！＆＃39; activerecord（4.0.5）lib / active_record / transactions.rb：269：在save' app/controllers/users_controller.rb:17:in创建＆＃39; actionpack（4.0.5）lib / action_controller / metal / implicit_render.rb：4：在send_action' actionpack (4.0.5) lib/abstract_controller/base.rb:189:in process_action＆＃39; actionpack（4.0.5）lib / action_controller / metal / rendering.rb：10：在process_action＆＃39;中的process_action' actionpack (4.0.5) lib/abstract_controller/callbacks.rb:18:in块中 activesupport（4.0.5）lib / active_support / callbacks.rb:403：在_run__2040789553997201778__process_action__callbacks' activesupport (4.0.5) lib/active_support/callbacks.rb:80:in run_callbacks＆＃39; actionpack（4.0.5）lib / abstract_controller / callbacks.rb:17:in process_action' actionpack (4.0.5) lib/action_controller/metal/rescue.rb:29:in process_action＆＃39; actionpack（4.0.5）lib / action_controller / metal / instrumentation.rb：31：在block in process_action' activesupport (4.0.5) lib/active_support/notifications.rb:159:in块中的仪器＆＃39; activesupport（4.0.5）lib / active_support / notifications / instrumenter.rb:20:in instrument' activesupport (4.0.5) lib/active_support/notifications.rb:159:in instrument＆＃39; actionpack（4.0.5）lib / action_controller / metal / instrumentation.rb：30：在process_action' actionpack (4.0.5) lib/action_controller/metal/params_wrapper.rb:250:in process_action＆＃39; activerecord（4.0.5）lib / active_record / railties / controller_runtime.rb:18:in process_action' actionpack (4.0.5) lib/abstract_controller/base.rb:136:in进程＆＃39; actionpack（4.0.5）lib / abstract_controller / rendering.rb：44：在process' actionpack (4.0.5) lib/action_controller/metal.rb:195:in dispatch＆＃39; actionpack（4.0.5）lib / action_controller / metal / rack_delegation.rb：13：dispatch' actionpack (4.0.5) lib/action_controller/metal.rb:231:in阻止行动＆＃39; actionpack（4.0.5）lib / action_dispatch / routing / route_set.rb:80:in call' actionpack (4.0.5) lib/action_dispatch/routing/route_set.rb:80:in dispatch＆＃39; 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Answer 1

读取堆栈跟踪，它告诉你什么是错的。看看你的User课程。也许你有类似的东西：

validates_presence_of :username

或

validates :username, presence: true