未初始化的常量误差常数技能：描述

Question

我正在尝试制作表单并将技能和说明提交到数据库中。我差不多完成了，但是在提交我的信息之后我收到了这个错误：

NameError in SkillsController#create
uninitialized constant Skill::Description

它指向我控制器中的这个动作：

def create
  @skills = Skill.new(skill_params)
  if @skills.save
    redirect_to :action => 'index'
  else
    @skills = Skill.find(:all)
    render :action => 'new'
  end
end

我在底部有一个定义params的私有方法：

private

  def skill_params
  params.require(:skill).permit(:description)
  end

这是完整的堆栈跟踪：

   activerecord (4.1.2.rc1) lib/active_record/inheritance.rb:133:in `compute_type'
    activerecord (4.1.2.rc1) lib/active_record/reflection.rb:221:in `klass'
    activerecord (4.1.2.rc1) lib/active_record/associations/association.rb:214:in `raise_on_type_mismatch!'
    activerecord (4.1.2.rc1) lib/active_record/associations/collection_association.rb:356:in `block in replace'
    activerecord (4.1.2.rc1) lib/active_record/associations/collection_association.rb:356:in `each_char'
    activerecord (4.1.2.rc1) lib/active_record/associations/collection_association.rb:356:in `replace'
    activerecord (4.1.2.rc1) lib/active_record/associations/collection_association.rb:41:in `writer'
    activerecord (4.1.2.rc1) lib/active_record/associations/builder/association.rb:118:in `description='
    activerecord (4.1.2.rc1) lib/active_record/attribute_assignment.rb:45:in `public_send'
    activerecord (4.1.2.rc1) lib/active_record/attribute_assignment.rb:45:in `_assign_attribute'
    activerecord (4.1.2.rc1) lib/active_record/attribute_assignment.rb:32:in `block in assign_attributes'
    activerecord (4.1.2.rc1) lib/active_record/attribute_assignment.rb:26:in `each'
    activerecord (4.1.2.rc1) lib/active_record/attribute_assignment.rb:26:in `assign_attributes'
    activerecord (4.1.2.rc1) lib/active_record/core.rb:455:in `init_attributes'
    activerecord (4.1.2.rc1) lib/active_record/core.rb:198:in `initialize'
    activerecord (4.1.2.rc1) lib/active_record/inheritance.rb:30:in `new'
    activerecord (4.1.2.rc1) lib/active_record/inheritance.rb:30:in `new'
    app/controllers/skills_controller.rb:29:in `create'
    actionpack (4.1.2.rc1) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
    actionpack (4.1.2.rc1) lib/abstract_controller/base.rb:189:in `process_action'
    actionpack (4.1.2.rc1) lib/action_controller/metal/rendering.rb:10:in `process_action'
    actionpack (4.1.2.rc1) lib/abstract_controller/callbacks.rb:20:in `block in process_action'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:113:in `call'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:113:in `call'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:229:in `block in halting'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:229:in `call'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:229:in `block in halting'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:166:in `call'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:166:in `block in halting'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:166:in `call'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:166:in `block in halting'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:166:in `call'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:166:in `block in halting'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:86:in `call'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:86:in `run_callbacks'
    actionpack (4.1.2.rc1) lib/abstract_controller/callbacks.rb:19:in `process_action'
    actionpack (4.1.2.rc1) lib/action_controller/metal/rescue.rb:29:in `process_action'
    actionpack (4.1.2.rc1) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
    activesupport (4.1.2.rc1) lib/active_support/notifications.rb:159:in `block in instrument'
    activesupport (4.1.2.rc1) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
    activesupport (4.1.2.rc1) lib/active_support/notifications.rb:159:in `instrument'
    actionpack (4.1.2.rc1) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
    actionpack (4.1.2.rc1) lib/action_controller/metal/params_wrapper.rb:250:in `process_action'
    activerecord (4.1.2.rc1) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
    actionpack (4.1.2.rc1) lib/abstract_controller/base.rb:136:in `process'
    actionview (4.1.2.rc1) lib/action_view/rendering.rb:30:in `process'
    actionpack (4.1.2.rc1) lib/action_controller/metal.rb:196:in `dispatch'
    actionpack (4.1.2.rc1) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
    actionpack (4.1.2.rc1) lib/action_controller/metal.rb:232:in `block in action'
    actionpack (4.1.2.rc1) lib/action_dispatch/routing/route_set.rb:82:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/routing/route_set.rb:82:in `dispatch'
    actionpack (4.1.2.rc1) lib/action_dispatch/routing/route_set.rb:50:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/journey/router.rb:71:in `block in call'
    actionpack (4.1.2.rc1) lib/action_dispatch/journey/router.rb:59:in `each'
    actionpack (4.1.2.rc1) lib/action_dispatch/journey/router.rb:59:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/routing/route_set.rb:678:in `call'
    warden (1.2.3) lib/warden/manager.rb:35:in `block in call'
    warden (1.2.3) lib/warden/manager.rb:34:in `catch'
    warden (1.2.3) lib/warden/manager.rb:34:in `call'
    rack (1.5.2) lib/rack/etag.rb:23:in `call'
    rack (1.5.2) lib/rack/conditionalget.rb:35:in `call'
    rack (1.5.2) lib/rack/head.rb:11:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/middleware/flash.rb:254:in `call'
    rack (1.5.2) lib/rack/session/abstract/id.rb:225:in `context'
    rack (1.5.2) lib/rack/session/abstract/id.rb:220:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/middleware/cookies.rb:560:in `call'
    activerecord (4.1.2.rc1) lib/active_record/query_cache.rb:36:in `call'
    activerecord (4.1.2.rc1) lib/active_record/connection_adapters/abstract/connection_pool.rb:621:in `call'
    activerecord (4.1.2.rc1) lib/active_record/migration.rb:380:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
    activesupport (4.1.2.rc1) lib/active_support/callbacks.rb:82:in `run_callbacks'
    actionpack (4.1.2.rc1) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/middleware/reloader.rb:73:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
    railties (4.1.2.rc1) lib/rails/rack/logger.rb:38:in `call_app'
    railties (4.1.2.rc1) lib/rails/rack/logger.rb:20:in `block in call'
    activesupport (4.1.2.rc1) lib/active_support/tagged_logging.rb:68:in `block in tagged'
    activesupport (4.1.2.rc1) lib/active_support/tagged_logging.rb:26:in `tagged'
    activesupport (4.1.2.rc1) lib/active_support/tagged_logging.rb:68:in `tagged'
    railties (4.1.2.rc1) lib/rails/rack/logger.rb:20:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/middleware/request_id.rb:21:in `call'
    rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
    rack (1.5.2) lib/rack/runtime.rb:17:in `call'
    activesupport (4.1.2.rc1) lib/active_support/cache/strategy/local_cache_middleware.rb:26:in `call'
    rack (1.5.2) lib/rack/lock.rb:17:in `call'
    actionpack (4.1.2.rc1) lib/action_dispatch/middleware/static.rb:64:in `call'
    rack (1.5.2) lib/rack/sendfile.rb:112:in `call'
    railties (4.1.2.rc1) lib/rails/engine.rb:514:in `call'

railties (4.1.2.rc1) lib/rails/application.rb:144:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
rack (1.5.2) lib/rack/content_length.rb:14:in `call'
rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
C:/RailsInstaller/Ruby2.0.0/lib/ruby/2.0.0/webrick/httpserver.rb:138:in `service'
C:/RailsInstaller/Ruby2.0.0/lib/ruby/2.0.0/webrick/httpserver.rb:94:in `run'
C:/RailsInstaller/Ruby2.0.0/lib/ruby/2.0.0/webrick/server.rb:295:in `block in start_thread'

这是我的架构：

  create_table "skills", force: true do |t|
    t.datetime "created_at"
    t.string   "description"
  end

这是我的技能/ new.html.erb表格：

<h1>Add new Skill</h1>
<%= form_tag ({action: "create"}) do %>
<p><label for="skill">Skill</label>:
<%= text_field 'skill', 'title' %></p>

<p><label for="skill_description">Description</label><br/>
<%= text_area 'skill', 'description' %></p>
<%= submit_tag "Create" %>
<% end  %>
<%= link_to 'Back', {:action => 'index'} %>

我希望我已经提供了足够的信息来解决这个问题，并感谢任何知道该做什么来初始化描述的人。再次感谢和欢呼！

index.html.erb：

<% if @skills.blank? %>
  <p>There are not any skills currently saved in the system.</p>
<% else %>
  <p>These are the current skills saved in our system</p>
  <ul id="skills">
    <% @skills.each do |c| %>
      <li><%= link_to c.title, {:action => 'show', :id => c.id} -%></li>
      <li>
       <%= link_to c.title, {:action => 'show', :id => c.id} -%>
       <b> <%= link_to 'Edit', {:action => 'edit', :id => c.id} %></b>
       <b> <%= link_to "Delete", {:action => 'delete', :id => c.id},
        :confirm => "Are you sure you want to delete this skill??" %></b>
      </li>
    <% end %>
  </ul>
  <p><%= link_to "Add new Skill", {:action => 'new' }%></p>
<% end %>

我没有可用的标题参数，这会导致问题。

skill.rb：

 class Skill < ActiveRecord::Base
    has_many :skill

    has_many :description
end

希望这些新信息有所帮助！再次感谢您一起来看看。

Answer 1

我认为您最好使用form_for。如果您以这种方式构建表单，则不会返回skill_params。

form_tag对于没有模型形式更好。

试试这样：

# skills_controller
def new
  @skill = Skill.new
end


# new.html.erb
<%= form_for @skill do |f| %>
  <%= f.text_area :description %>
   # Other fields and tags...
  <%= f.submit %>
<% end %> 

希望这有帮助。

Answer 2

将模型 skill.rb 更改为：

class Skill < ActiveRecord::Base
end

has_many方法用于在ORM上下文中定义Relations。无需定义表本身的列。 Rails自己获取这些信息。

您的index.html.erb和new.html.erb页面中还有其他问题。您指的是title skill属性，但您的迁移未显示title属性。

我建议您删除控制器，模型，视图，迁移和数据表本身（假设它只是一个开发项目）并使用scaffold使用以下命令生成它们：

$ bin/rails generate scaffold Skill title:string description:text

请注意$不是命令的一部分，而是终端中的提示。

Read up more on rails command line here