Rails + CarrierWave: NoMethodError: undefined method `name' for nil:NilClass

问题

I am using CarrierWave with Rails 3.1. I am getting the following error message when I submit the form (trying to upload an image):

Error Message:

ActiveRecord::StatementInvalid in Admin::PostsController#create

NoMethodError: undefined method `name' for nil:NilClass: INSERT INTO "posts" ("body", "created_at", "draft", "image", "post_type", "title", "updated_at", "user_id") VALUES (?, ?, ?, ?, ?, ?, ?, ?)
Rails.root: /Users/aziz/Sandbox/ruby/rails/Tumblelog

Application Trace | Framework Trace | Full Trace
app/controllers/admin/posts_controller.rb:18:in `create'
Request

Parameters:

{"utf8"=>"✓",
 "authenticity_token"=>"za+zNRDGNCcujnCmO726cWCo2ze1rgaXv5bL17JGaek=",
 "post"=>{"image"=>#<ActionDispatch::Http::UploadedFile:0x000001014aeff0 @original_filename="AzizLight.jpeg",
 @content_type="image/jpeg",
 @headers="Content-Disposition: form-data; name=\"post[image]\"; filename=\"AzizLight.jpeg\"\r\nContent-Type: image/jpeg\r\n",
 @tempfile=#<File:/var/folders/ky/2ddtbt0d7k1g__2ctr8njcfc0000gn/T/RackMultipart20110918-21704-hp2ajt>>,
 "draft"=>"0",
 "user_id"=>"2",
 "post_type"=>"image"},
 "commit"=>"Post"}

The problem is that I don't know where this name comes from and I don't know what variable is being nil, so I can't debug properly (I tried to debug a log before asking here). Line 18 corresponds to the @post.save line in the following controller:

PostsController:

# ...

def new
  @post = Post.new
  @form_html_options = (params[:post_type] == "image") ? { :multipart => true } : {}
  @form_partial = get_form_partial(params[:post_type])
  redirect_to admin_posts_path, :alert => "You tried to create an unknown type of post..." if @form_partial.nil?
  @title = "Creating a new post..."
end

def create
  @post = Post.new(params[:post])
  if @post.save
    flash[:success] = "Post created successfully!"
    redirect_to admin_post_path(@post)
  else
    @title = "Creating a new post..."
    @form_partial = get_form_partial(params[:post][:post_type])
    render 'new'
  end
end

# ...

Here other files that might be needed to spot the problem:

Post (model):

attr_accessible :title, :body, :user_id, :draft, :post_type, :image

belongs_to :user

mount_uploader :image_url, ImageUploader

ImageUploader:

class ImageUploader < CarrierWave::Uploader::Base
  include CarrierWave::RMagick

  storage :fog

  def extension_white_list
    %w(jpg jpeg gif png)
  end
end

new.html.erb:

<h1><%= @title %></h1>

<%= form_for @post, :url => admin_posts_path, :html => @form_html_options do |f| %>
  <%= render 'form', :f => f %>
<% end %>

_form.html.erb:

<%= render 'error_messages' %>

<%= render @form_partial, :f => f %>

<p class="drop-down">
  <%= f.label :draft, 'Status' %>
  <%= f.select(:draft, options_for_select([["Published", 0], ["Draft", 1]], (@post.new_record? ? 0: @post.draft))) %>
</p>

<%= f.hidden_field :user_id, :value => @post.user_id || current_user.id %>
<%= f.hidden_field :post_type, :value => @post.post_type || params[:post_type] %>

<p class="button"><%= f.submit "Post", :disable_with => 'Posting...' %></p>

_image_form.html.erb (@form_partial):

<p><%= f.file_field :image %></p>

So what it really going on please?

回答1:

Your image uploader class was not loaded into your current rails server thread. Reload rails server and it should work fine =).

回答2:

Make sure you use - mount_uploader :image, ImageUploader in your model like here -

class CarImage < ActiveRecord::Base 
  belongs_to :car
  mount_uploader :image, ImageUploader
end

Regards

Robbie

回答3:

I experienced the some problem and the cause is (probably always) that the UploadedFile object has been sent to the attribute carrierwave was mounted on. The db adapter cannot serialize this object and will therefore throw this error.

Make sure that:

the uploader has been properly mounted
you don't use write_attribute to write the uploaded file (which was the cause of my problem). Use the accessor instead: model.send('image=', params[:model][:image]). Uglier, but better.

回答4:

Make sure in your model:

mount_uploader :image, ImageLoader

Remember that :image must be the string/text type.

回答5:

I came across this post because I had the same error you described, but restarting the server didn't resolve it (as suggested by other answers). In my case, the problem was caused because I used mount_uploader before attr_accessible. By switching them I solved the problem.

回答6:

I had a similar problem. Solution was changing:

attr_accessible :title, :body, :user_id, :draft, :post_type, :image
belongs_to :user
mount_uploader :image_url, ImageUploader

to:

attr_accessible :title, :body, :user_id, :draft, :post_type, :image_url
belongs_to :user
mount_uploader :image_url, ImageUploader

来源：https://stackoverflow.com/questions/7464536/rails-carrierwave-nomethoderror-undefined-method-name-for-nilnilclass

标签

ruby-on-rails

carrierwave

nomethoderror