ruby-on-rails - 添加 :multipart => true throws Undefined Method "name" error

Question

我在这上面画了一个空白。这是我的问题:

精简版

我的 image#create 操作在调用 image.save 时失败并抛出 Undefined method "name"for nil:NilClass。 Image 模型包括通过 paperclip gem 上传文件。

让我失望的部分:

只有当我在提交表单中包含 :multipart => true 时才会出现错误

当我将其删除时，表单可以正常工作，当然图像文件不会上传。有关失败位置的详细信息，请参阅下面的堆栈跟踪。看起来它在尝试为 INSERT 语句引用某些内容时达到了 nil 值，但我不知道是什么。我的 Controller 参数看起来没问题，我通过记录器检查以确保新的 Image 实例在它点击保存调用之前正确构建。

额外细节

我会尽量包括我能想到的所有细节，按重要性排序:

• 我正在使用 paperclip并尝试通过 S3 存储，尽管当我完全注释掉图像模型中的 has_attached_file 行时仍然会出现此问题。

• Image 是 Collection 中的嵌套资源，由 to_param 方法中的 slug 引用。

• 我掌握了 Multi-Tenancy 系统的基础知识(又名 Basecamp 风格的用户子域，通过涵盖所有组件的中央用户模型实现)。

传递给 Controller ​​的参数

{"utf8"=>"✓",
 "authenticity_token"=>"JYCMky7851j5cW4ChSWUCCL/02iePf6i/QWAgR8q5tE=",
 "image"=>{"name"=>"My testerific image 2",
 "slug"=>"my-testerific-image-2",
 "description"=>"w",
 "collection_id"=>"2",
 "sort"=>"3",
 "picture_file_name"=>#<ActionDispatch::Http::UploadedFile:0x00000101b3f540 @original_filename="David's pic 005.jpeg",
 @content_type="image/jpeg",
 @headers="Content-Disposition: form-data; name=\"image[picture_file_name]\"; filename=\"David's pic 005.jpeg\"\r\nContent-Type: image/jpeg\r\n",
 @tempfile=#<File:/var/folders/df/mvsv5cs137gbyl8r7h428zp40000gn/T/RackMultipart20110814-64770-duz6wu>>},
 "commit"=>"Create Image",
 "collection_id"=>"my-new-collection"}

完整堆栈跟踪

activesupport (3.0.9) lib/active_support/whiny_nil.rb:48:in 'method_missing'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:20:in 'block in initialize'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in 'yield'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in 'default'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in 'block in initialize'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in 'yield'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in 'default'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in 'block in initialize'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in 'yield'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in 'default'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in 'block in initialize'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in 'yield'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in 'default'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:22:in 'block in initialize'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:63:in 'yield'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:63:in 'default'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:63:in 'accept'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:325:in 'block in dump_ivars'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:323:in 'each'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:323:in 'dump_ivars'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:85:in 'visit_Object'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:63:in 'accept'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:36:in '<<'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych.rb:165:in 'dump'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/psych/core_ext.rb:13:in 'psych_to_yaml'
activerecord (3.0.9) lib/active_record/connection_adapters/abstract/quoting.rb:34:in 'quote'
activerecord (3.0.9) lib/active_record/connection_adapters/sqlite3_adapter.rb:45:in 'quote'
arel (2.0.10) lib/arel/visitors/to_sql.rb:327:in 'quote'
arel (2.0.10) lib/arel/visitors/to_sql.rb:70:in 'block in visit_Arel_Nodes_Values'
arel (2.0.10) lib/arel/visitors/to_sql.rb:69:in 'map'
arel (2.0.10) lib/arel/visitors/to_sql.rb:69:in 'visit_Arel_Nodes_Values'
arel (2.0.10) lib/arel/visitors/visitor.rb:15:in 'visit'
arel (2.0.10) lib/arel/visitors/to_sql.rb:59:in 'visit_Arel_Nodes_InsertStatement'
arel (2.0.10) lib/arel/visitors/visitor.rb:15:in 'visit'
arel (2.0.10) lib/arel/visitors/visitor.rb:5:in 'accept'
arel (2.0.10) lib/arel/visitors/to_sql.rb:18:in 'block in accept'
activerecord (3.0.9) lib/active_record/connection_adapters/abstract/connection_pool.rb:111:in 'with_connection'
arel (2.0.10) lib/arel/visitors/to_sql.rb:16:in 'accept'
arel (2.0.10) lib/arel/tree_manager.rb:20:in 'to_sql'
arel (2.0.10) lib/arel/select_manager.rb:217:in 'insert'
activerecord (3.0.9) lib/active_record/relation.rb:14:in 'insert'
activerecord (3.0.9) lib/active_record/persistence.rb:274:in 'create'
activerecord (3.0.9) lib/active_record/timestamp.rb:47:in 'create'
activerecord (3.0.9) lib/active_record/callbacks.rb:277:in 'block in create'
activesupport (3.0.9) lib/active_support/callbacks.rb:414:in '_run_create_callbacks'
activerecord (3.0.9) lib/active_record/callbacks.rb:277:in 'create'
activerecord (3.0.9) lib/active_record/persistence.rb:250:in 'create_or_update'
activerecord (3.0.9) lib/active_record/callbacks.rb:273:in 'block in create_or_update'
activesupport (3.0.9) lib/active_support/callbacks.rb:429:in '_run_save_callbacks'
activerecord (3.0.9) lib/active_record/callbacks.rb:273:in 'create_or_update'
activerecord (3.0.9) lib/active_record/persistence.rb:40:in 'save'
activerecord (3.0.9) lib/active_record/validations.rb:43:in 'save'
activerecord (3.0.9) lib/active_record/attribute_methods/dirty.rb:21:in 'save'
activerecord (3.0.9) lib/active_record/transactions.rb:240:in 'block (2 levels) in save'
activerecord (3.0.9) lib/active_record/transactions.rb:292:in 'block in with_transaction_returning_status'
activerecord (3.0.9) lib/active_record/connection_adapters/abstract/database_statements.rb:139:in 'transaction'
activerecord (3.0.9) lib/active_record/transactions.rb:207:in 'transaction'
activerecord (3.0.9) lib/active_record/transactions.rb:290:in 'with_transaction_returning_status'
activerecord (3.0.9) lib/active_record/transactions.rb:240:in 'block in save'
activerecord (3.0.9) lib/active_record/transactions.rb:251:in 'rollback_active_record_state!'
activerecord (3.0.9) lib/active_record/transactions.rb:239:in 'save'
app/controllers/images_controller.rb:42:in 'block in create'
actionpack (3.0.9) lib/action_controller/metal/mime_responds.rb:264:in 'call'
actionpack (3.0.9) lib/action_controller/metal/mime_responds.rb:264:in 'retrieve_response_from_mimes'
actionpack (3.0.9) lib/action_controller/metal/mime_responds.rb:191:in 'respond_to'
app/controllers/images_controller.rb:40:in 'create'
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 'block in process_action'
activesupport (3.0.9) lib/active_support/callbacks.rb:451:in '_run__867212960703161301__process_action__2360218484576085785__callbacks'
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 '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 'block in process_action'
activesupport (3.0.9) lib/active_support/notifications.rb:52:in 'block 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 'block 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 'block in call'
rack-mount (0.6.14) lib/rack/mount/code_generation.rb:93:in 'block in recognize'
rack-mount (0.6.14) lib/rack/mount/code_generation.rb:68: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'
warden (1.0.5) lib/warden/manager.rb:35:in 'block in call'
warden (1.0.5) lib/warden/manager.rb:34:in 'catch'
warden (1.0.5) lib/warden/manager.rb:34: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 'block 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 'block 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 'block in call'
<internal:prelude>:10: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 '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'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/webrick/httpserver.rb:111:in 'service'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/webrick/httpserver.rb:70:in 'run'
/Users/daw/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/webrick/server.rb:183:in 'block in start_thread'

更新

根据要求，型号代码:

class Image < ActiveRecord::Base
  belongs_to :collection
  belongs_to :user

  before_save :create_slug

  has_attached_file :picture,
    #:styles => { 
        #   :thumb => '100x100>', 
        #   :full => '800x800>' 
        #},
        :storage => :s3,
        :s3_credentials => Rails.root.join( 'config', 's3.yml' ),
        :path => ":id/:style/:filename"


  def to_param
    self.name.parameterize
  end
  private
  def create_slug
    self.slug = self.to_param
  end
end

更新2

我比较了使用 :multipart => true 和没有构建的 Image 实例，确认唯一的区别是文件上传字段，picture_file_name 。如果没有 :multipart => true，它是一个带有文件名的字符串(不足为奇)。有了它，它就是 ActionDispatch::Http::UploadedFile 的一个实例。鉴于堆栈跟踪显示它在 to_yaml 调用期间失败，也许问题在于 UploadedFile 实例转换为 YAML？

Answer 1

好吧，我终于放下心来，通过记录器输出追踪了 ActiveRecord 源代码。结果，正如我所怀疑的那样，它未能保存 UploadedFile，因为它无法将其转换为 YAML。

但是，这是因为我犯了一个愚蠢的错误。在我的提交表单中，我有:

<%= f.file_field :picture_file_name %>

应该是什么时候:

<%= f.file_field :picture %>

paperclip gem 理解 :picture 是上传的文件，并使用后台魔法将文件名保存到正确的字段。我只是低估了我猜的易用性!

通常，我会删除这种微不足道的问题，但鉴于我犯了这个错误，将来其他人可能会这样做，而且几乎没有什么可以指出我的解决方案。因此，我会继续关注它，以帮助将来在谷歌上搜索同样密集的开发人员!