Question

I get an error that look like this:

undefined method `post_image_will_change!' for #<Post:0xf4e9184>
app/controllers/posts_controller.rb:43:in `new'
app/controllers/posts_controller.rb:43:in `create'

I’ve included this in my “post” model:

 attr_accessible :title, :name, :content, :post_image
 mount_uploader :post_image, PostImageUploader

and in _form.html.erb I’ve added:

 :html =>  { :multipart => true }

I looked CarrierWave Error but that doesn’t help me.

Any clues of what generates that error? I’ve migrated the database and so forth (followed the railscasts guide on carrierwave exactly..)

Answer 1

The OP comments that he fixed it, however there’s no answer set so I thought I’d add one for people coming across this in the future, which included myself until I figured it out 🙂

undefined method `x_will_change!’ for # happens if you forget to add a column in your model’s db table. If you have a model User and a AvatarUploader, with the uploader mounted as in the Carrierwave docs:

class User < ActiveRecord::Base
  mount_uploader :avatar, AvatarUploader
end

Then the error will read

undefined method `avatar_will_change!' for #<User:0x00...>

To fix it (based on this example) add a column in a migration run the following in the console:

rails g migration AddAvatarToUsers avatar:string

This will generate the following migration:

class AddAvatarToUsers < ActiveRecord::Migration
  def change
    add_column :users, :avatar, :string
  end
end

Then migrate to apply the change (again in the console):

rake db:migrate