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Ruby on rails 用户中的命名错误#新增

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Ruby on rails 用户中的命名错误#新增,ruby-on-rails,Ruby On Rails,我开始出现以下错误： NoMethodError: undefined method `has_key?' for nil:NilClass 在即将完成Hartl的优秀Rails教程的过程中。看起来我一定漏掉了一个方法，但我知道在哪里，而且我还不熟悉Rails中的调试 以下是完整的堆栈跟踪： activerecord (3.0.9) lib/active_record/attribute_methods/read.rb:80:in `id' activerecord (3.0.9) lib/a

我开始出现以下错误：

NoMethodError: undefined method `has_key?' for nil:NilClass
在即将完成Hartl的优秀Rails教程的过程中。看起来我一定漏掉了一个方法，但我知道在哪里，而且我还不熟悉Rails中的调试

以下是完整的堆栈跟踪：

activerecord (3.0.9) lib/active_record/attribute_methods/read.rb:80:in `id'
activerecord (3.0.9) lib/active_record/attribute_methods/primary_key.rb:9:in `to_key'
actionpack (3.0.9) lib/action_controller/record_identifier.rb:82:in `record_key_for_dom_id'
actionpack (3.0.9) lib/action_controller/record_identifier.rb:63:in `dom_id'
actionpack (3.0.9) lib/action_view/helpers/form_helper.rb:331:in `apply_form_for_options!'
actionpack (3.0.9) lib/action_view/helpers/form_helper.rb:313:in `form_for'
app/views/users/new.html.erb:3:in `_app_views_users_new_html_erb___834068491__620833808_0'
actionpack (3.0.9) lib/action_view/template.rb:135:in `send'
actionpack (3.0.9) lib/action_view/template.rb:135:in `render'
activesupport (3.0.9) lib/active_support/notifications.rb:54:in `instrument'
actionpack (3.0.9) lib/action_view/template.rb:127:in `render'
actionpack (3.0.9) lib/action_view/render/rendering.rb:59:in `_render_template'
activesupport (3.0.9) lib/active_support/notifications.rb:52:in `instrument'
activesupport (3.0.9) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.0.9) lib/active_support/notifications.rb:52:in `instrument'
actionpack (3.0.9) lib/action_view/render/rendering.rb:56:in `_render_template'
actionpack (3.0.9) lib/action_view/render/rendering.rb:26:in `render'
actionpack (3.0.9) lib/abstract_controller/rendering.rb:115:in `_render_template'
actionpack (3.0.9) lib/abstract_controller/rendering.rb:109:in `render_to_body'
actionpack (3.0.9) lib/action_controller/metal/renderers.rb:47:in `render_to_body'
actionpack (3.0.9) lib/action_controller/metal/compatibility.rb:55:in `render_to_body'
actionpack (3.0.9) lib/abstract_controller/rendering.rb:102:in `render_to_string'
actionpack (3.0.9) lib/abstract_controller/rendering.rb:93:in `render'
actionpack (3.0.9) lib/action_controller/metal/rendering.rb:17:in `render'
actionpack (3.0.9) lib/action_controller/metal/instrumentation.rb:40:in `render'
activesupport (3.0.9) lib/active_support/core_ext/benchmark.rb:5:in `ms'
/usr/lib/ruby/1.8/benchmark.rb:308:in `realtime'
activesupport (3.0.9) lib/active_support/core_ext/benchmark.rb:5:in `ms'
actionpack (3.0.9) lib/action_controller/metal/instrumentation.rb:40:in `render'
actionpack (3.0.9) lib/action_controller/metal/instrumentation.rb:78:in `cleanup_view_runtime'
activerecord (3.0.9) lib/active_record/railties/controller_runtime.rb:15:in `cleanup_view_runtime'
actionpack (3.0.9) lib/action_controller/metal/instrumentation.rb:39:in `render'
actionpack (3.0.9) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
actionpack (3.0.9) lib/action_controller/metal/mime_responds.rb:261:in `retrieve_response_from_mimes'
actionpack (3.0.9) lib/action_controller/metal/mime_responds.rb:192:in `call'
actionpack (3.0.9) lib/action_controller/metal/mime_responds.rb:192:in `respond_to'
app/controllers/users_controller.rb:29:in `new'
actionpack (3.0.9) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (3.0.9) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (3.0.9) lib/abstract_controller/base.rb:150:in `process_action'
actionpack (3.0.9) lib/action_controller/metal/rendering.rb:11:in `process_action'
actionpack (3.0.9) lib/abstract_controller/callbacks.rb:18:in `process_action'
activesupport (3.0.9) lib/active_support/callbacks.rb:436:in `_run__434435962__process_action__943997142__callbacks'
activesupport (3.0.9) lib/active_support/callbacks.rb:410:in `send'
activesupport (3.0.9) lib/active_support/callbacks.rb:410:in `_run_process_action_callbacks'
activesupport (3.0.9) lib/active_support/callbacks.rb:94:in `send'
activesupport (3.0.9) lib/active_support/callbacks.rb:94:in `run_callbacks'
actionpack (3.0.9) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.0.9) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
activesupport (3.0.9) lib/active_support/notifications.rb:52:in `instrument'
activesupport (3.0.9) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.0.9) lib/active_support/notifications.rb:52:in `instrument'
actionpack (3.0.9) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.0.9) lib/action_controller/metal/rescue.rb:17:in `process_action'
actionpack (3.0.9) lib/abstract_controller/base.rb:119:in `process'
actionpack (3.0.9) lib/abstract_controller/rendering.rb:41:in `process'
actionpack (3.0.9) lib/action_controller/metal.rb:138:in `dispatch'
actionpack (3.0.9) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.0.9) lib/action_controller/metal.rb:178:in `action'
actionpack (3.0.9) lib/action_dispatch/routing/route_set.rb:62:in `call'
actionpack (3.0.9) lib/action_dispatch/routing/route_set.rb:62:in `dispatch'
actionpack (3.0.9) lib/action_dispatch/routing/route_set.rb:27:in `call'
rack-mount (0.6.14) lib/rack/mount/route_set.rb:148:in `call'
rack-mount (0.6.14) lib/rack/mount/code_generation.rb:93:in `recognize'
rack-mount (0.6.14) lib/rack/mount/code_generation.rb:103:in `optimized_each'
rack-mount (0.6.14) lib/rack/mount/code_generation.rb:92:in `recognize'
rack-mount (0.6.14) lib/rack/mount/route_set.rb:139:in `call'
actionpack (3.0.9) lib/action_dispatch/routing/route_set.rb:493:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/head.rb:14:in `call'
rack (1.2.3) lib/rack/methodoverride.rb:24:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/flash.rb:182:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/session/abstract_store.rb:149:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/cookies.rb:302:in `call'
activerecord (3.0.9) lib/active_record/query_cache.rb:32:in `call'
activerecord (3.0.9) lib/active_record/connection_adapters/abstract/query_cache.rb:28:in `cache'
activerecord (3.0.9) lib/active_record/query_cache.rb:12:in `cache'
activerecord (3.0.9) lib/active_record/query_cache.rb:31:in `call'
activerecord (3.0.9) lib/active_record/connection_adapters/abstract/connection_pool.rb:354:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/callbacks.rb:46:in `call'
activesupport (3.0.9) lib/active_support/callbacks.rb:416:in `_run_call_callbacks'
actionpack (3.0.9) lib/action_dispatch/middleware/callbacks.rb:44:in `call'
rack (1.2.3) lib/rack/sendfile.rb:107:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/remote_ip.rb:48:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/show_exceptions.rb:47:in `call'
railties (3.0.9) lib/rails/rack/logger.rb:13:in `call'
rack (1.2.3) lib/rack/runtime.rb:17:in `call'
activesupport (3.0.9) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.2.3) lib/rack/lock.rb:11:in `call'
rack (1.2.3) lib/rack/lock.rb:11:in `synchronize'
rack (1.2.3) lib/rack/lock.rb:11:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/static.rb:30:in `call'
railties (3.0.9) lib/rails/application.rb:168:in `call'
railties (3.0.9) lib/rails/application.rb:77:in `send'
railties (3.0.9) lib/rails/application.rb:77:in `method_missing'
railties (3.0.9) lib/rails/rack/log_tailer.rb:14:in `call'
rack (1.2.3) lib/rack/content_length.rb:13:in `call'
rack (1.2.3) lib/rack/handler/webrick.rb:52:in `service'
/usr/lib/ruby/1.8/webrick/httpserver.rb:104:in `service'
/usr/lib/ruby/1.8/webrick/httpserver.rb:65:in `run'
/usr/lib/ruby/1.8/webrick/server.rb:173:in `start_thread'
/usr/lib/ruby/1.8/webrick/server.rb:162:in `start'
/usr/lib/ruby/1.8/webrick/server.rb:162:in `start_thread'
/usr/lib/ruby/1.8/webrick/server.rb:95:in `start'
/usr/lib/ruby/1.8/webrick/server.rb:92:in `each'
/usr/lib/ruby/1.8/webrick/server.rb:92:in `start'
/usr/lib/ruby/1.8/webrick/server.rb:23:in `start'
/usr/lib/ruby/1.8/webrick/server.rb:82:in `start'
rack (1.2.3) lib/rack/handler/webrick.rb:13:in `run'
rack (1.2.3) lib/rack/server.rb:217:in `start'
railties (3.0.9) lib/rails/commands/server.rb:65:in `start'
railties (3.0.9) lib/rails/commands.rb:30
railties (3.0.9) lib/rails/commands.rb:27:in `tap'
railties (3.0.9) lib/rails/commands.rb:27
script/rails:6:in `require'
script/rails:6
我可以看出错误是因为在登录过程中没有创建用户。 所以我进入控制台，试图创建一个用户；以下是该错误堆栈：

from script/rails:6irb(main):004:0> user=User.new
NoMethodError: undefined method `has_key?' for nil:NilClass
    from /usr/lib/ruby/gems/1.8/gems/activesupport-3.0.9/lib/active_support/whiny_nil.rb:48:in `method_missing'
    from /usr/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/active_record/base.rb:1512:in `has_attribute?'
    from /usr/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/active_record/base.rb:1672:in `inspect'
    from /usr/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/active_record/base.rb:1671:in `collect'
    from /usr/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/active_record/base.rb:1671:in `inspect'
    from /usr/lib/ruby/1.8/irb.rb:310:in `output_value'
    from /usr/lib/ruby/1.8/irb.rb:159:in `eval_input'
    from /usr/lib/ruby/1.8/irb.rb:271:in `signal_status'
    from /usr/lib/ruby/1.8/irb.rb:155:in `eval_input'
    from /usr/lib/ruby/1.8/irb.rb:154:in `eval_input'
    from /usr/lib/ruby/1.8/irb.rb:71:in `start'
    from /usr/lib/ruby/1.8/irb.rb:70:in `catch'
    from /usr/lib/ruby/1.8/irb.rb:70:in `start'
    from /usr/lib/ruby/gems/1.8/gems/railties-3.0.9/lib/rails/commands/console.rb:44:in `start'
    from /usr/lib/ruby/gems/1.8/gems/railties-3.0.9/lib/rails/commands/console.rb:8:in `start'
    from /usr/lib/ruby/gems/1.8/gems/railties-3.0.9/lib/rails/commands.rb:23
    from script/rails:6:in `require'
我使用的是Rails 3.0.9。如果有人能给我指出正确的方向，我会非常感激的

谢谢

瑞克 增设员额（2011年9月27日）：

为了帮助我的评论者——

是的，我已经迁移了我的数据库

我在教程中所处的位置：我基本上已经完成了教程，但不同于它如何编码用户，而是使用了脚手架，而不是Hartl所采用的增量方法

以下是users/new.html.erb：

<h1>New user</h1>

<%= form_for(@user) do |f| %>
  <div class="field">
    <%= f.label :firstname, "First Name" %><br />
    <%= f.text_field :firstname %>
  </div>
  <div class="field">
    <%= f.label :lastname, "Last Name" %><br />
    <%= f.text_field :lastname %>
  </div>
  <div class="field">
    <%= f.label :username %><br />
    <%= f.text_field :username %>
  </div>
  <div class="field">
    <%= f.label :email %><br />
    <%= f.text_field :email %>
  </div>
  <div class="field">
    <%= f.label :password %><br />
    <%= f.password_field :password %>
  </div>
  <div class="field">
    <%= f.label :password_confirmation, "Confirmation" %><br />
    <%= f.password_field :password_confirmation %>
  </div>
  <div class="actions">
    <%= f.submit "Sign up" %>
  </div>
<% end %>


<%= link_to 'Back', users_path %>

新用户
我认为导致我的bug的原因是，由于某种原因，模型没有创建用户对象；这就是为什么我会得到‘nil object’错误

非常感谢任何帮助

--rick

欢迎来到Rails并调试Rails程序

一些常规调试技巧

  • 虽然
    nil
    对象有许多方法，但它显然不是ActiveRecord对象，因此没有
    has\u key？
    方法

  • 所以问题是（正如您所猜测的）应该返回ActiveRecord对象的方法返回的是nil

  • 所以接下来要弄清楚原因。由于您试图创建ActiveRecord对象，很可能是该对象未通过验证。保存前使用
    valid？
    检查此项。或者使用
    保存
    而不是
    save
    The
    save方法将抛出错误
  • 了解如何在调试时使用logging语句将日志消息发送到日志文件

  • 您还可以使用交互式调试器。它可以设置为在浏览器的请求到达服务器中的特定代码行时调用。-在调试器中“继续”之前，浏览器将一直处于计时状态

添加了调试验证

为了调试验证，我使用了两种技术：

  • 不要试图使用调试器来跟踪验证的执行——正如您所看到的，这是一个纸上谈兵的游戏
  • 请使用调试器调用AR对象上的
    save
    或
    valid？
    方法。然后可以检查对象或使用方法查看AR对象中包含的错误对象。错误对象通常会告诉您哪个验证失败
  • 您还可以单独注释验证，直到找到给您带来问题的验证
  • 您还可以使用调试器检查AR对象的属性，以查看属性值是否将通过验证
  • 回复：验证何时运行（如您在评论中所问）。请记住，默认情况下，验证将在create调用和update调用上运行。如果希望仅在更新时（而不是在创建时）检查单个验证，有几种方法可以做到这一点，请检查文档中的单个验证
关于验证还有很多要说的。如果您有一个特定的验证失败了，并且您不理解它失败的原因，那么在SO中打开一个单独的问题

Re：为什么在创建时必须传递验证，而不仅仅是更新呢？——这是一个特性。它使您能够确保在数据库中只创建有效的对象。但你不必使用它。您可以将验证设置为仅在更新时处于活动状态

验证是ActiveRecord强大而复杂的一部分。换句话说，在理解它们之前，它们可能是复杂的。

欢迎来到Rails并调试Rails程序

一些常规调试技巧

  • 虽然
    nil
    对象有许多方法，但它显然不是ActiveRecord对象，因此没有
    has\u key？
    方法

  • 所以问题是（正如您所猜测的）应该返回ActiveRecord对象的方法返回的是nil

  • 所以接下来要弄清楚原因。由于您试图创建ActiveRecord对象，很可能是该对象未通过验证。保存前使用
    valid？
    检查此项。或者使用
    保存
    而不是
    save
    The
    save方法将抛出错误
  • 了解如何在调试时使用logging语句将日志消息发送到日志文件

  • 您还可以使用交互式调试器。它可以设置为在浏览器的请求到达服务器中的特定代码行时调用。-在调试器中“继续”之前，浏览器将一直处于计时状态

添加了调试验证

为了调试验证，我使用了两种技术：

  • 不要试图使用调试器来跟踪验证的执行——正如您所看到的，这是一个纸上谈兵的游戏
  • 请使用调试器调用AR对象上的
    save
    或
    valid？
    方法。然后可以检查对象或使用方法查看AR对象中包含的错误对象。错误对象通常会告诉您哪个验证失败
  • 您还可以单独注释验证，直到找到给您带来问题的验证
  • 您还可以使用调试器检查要修改的AR对象的属性 
    script/console

class User < ActiveRecord:Base

  def initialize

  end
end

User.new
=> NoMethodError: undefined method `has_key?' for nil:NilClass