Errors while using paperclip in rails app

问题

At the moment I try to replace attachment_fu fileuploading plugin with paperclip.

But there are some errors while uploading:

My controller looks like this:

def create
add_breadcrumb 'breadcrumb.upload_file', {:action => :new}

puts "BLUBBBBBBBBBBBBBBBBBBBBBBBBBBB"
puts params[:upload]

    @upload = Upload.create(params[:upload])
    @upload.lecturer_id = current_user.id
    if @upload.save
        flash[:notice] = I18n.t("flash.saved")
        redirect_to :action => :index
    else
        render :action => :new
    end
end

and my model like this:

puts has_attached_file :image, :default_url => :file_system
validates_attachment_content_type :image, :content_type => [:image, 'audio/mpeg', 'application/mp3', 'application/octet-stream']

While uploading I got this error:

ActiveRecord::UnknownAttributeError in UploadsController#create

unknown attribute: uploaded_data

app/controllers/uploads_controller.rb:24:in `create'

Update:

{"name"=>"TEST", "uploaded_data"=>#<ActionDispatch::Http::UploadedFile:0x00000005518a38 @original_filename="2014-09-26 18.14.22.jpg", @content_type="image/jpeg", @headers="Content-Disposition: form-data; name=\"upload[uploaded_data]\"; filename=\"2014-09-26 18.14.22.jpg\"\r\nContent-Type: image/jpeg\r\n", @tempfile=#<Tempfile:/tmp/RackMultipart20150415-12671-190wpi5>>}

Update: thats not that what I wanted. The migration generetad some new columns in database, how can I return to the previus version? is there a demigrate coammand?

回答1:

To revert the migration from Paperclip you can use either:

rake db:migrate:down VERSION=_current_migration_number

or

rake db:rollback

Until your previous state. Then you can create a new migration like this:

class ChangeUploadToPaperclip < ActiveRecord::Migration
  change do
    rename_column :uploads, :content_type, :upload_content_type 
    rename_column :uploads, :filename, :upload_filename
    rename_column :uploads, :size, :upload_file_size
    add_column :uploads, :upload_updated_at, :datetime
    # Warning: the following will remove your old data, irreversible.
    remove_column :uploads, :width 
    remove_column :uploads, :height 
    remove_column :uploads, :thumbnail 
  end
end

But there could be potential errors between your old storage and Paperclips way of storing files.

In this answer I assumed that your model has_attached_file :upload.

If you have another name for the attached file, update every upload and uploads accordingly.

Edit The migration file needs to have a certain name:

20150417125122_change_upload_to_paperclip.rb

(the date-string is auto generated, I copied this from comment below.)

This is because Rails will look for ChangeUploadToPaperclip only if there is underscore between.

If you have changeuploadtopaperclip.rb it would look for Changeuploadtopaperclip.

Running special migration

rake db:migrate:up VERSION=20150417125122

回答2:

your column for image is image from your model structure. But the data in params the image is coming in params[:model_name][uploaded_data]. Your model doesnt contain any column with name uploaded_data that too for a attached_file

In your form_for you should have this

= f.file_field :image

not

= f.file_field :uploaded_data

In this way your params would look like

{"name"=>"TEST", "image"=>#<ActionDispatch::Http::UploadedFile:0x00000005518a38 @original_filename="2014-09-26 18.14.22.jpg", @content_type="image/jpeg", @headers="Content-Disposition: form-data; name=\"upload[uploaded_data]\"; filename=\"2014-09-26 18.14.22.jpg\"\r\nContent-Type: image/jpeg\r\n", @tempfile=#<Tempfile:/tmp/RackMultipart20150415-12671-190wpi5>>}

And it wont give you any error

GO through the gem on github paperclip

You nee to create migration file like this:

class AddAvatarColumnsToUsers < ActiveRecord::Migration
  def self.up
    add_attachment :model_name, :[image]
  end

  def self.down
    remove_attachment :model_name, :[image]
  end
end

Or use the generator:

rails generate paperclip model_name [image]

来源：https://stackoverflow.com/questions/29647970/errors-while-using-paperclip-in-rails-app