carrierwave - rails 3.1- undefined method: image_will_change

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..)

manged to fix it.. had made an extreme rookie misstake. Ty anyway — buren, Oct 06 '11 at 15:31

score 133 · Accepted Answer · answered May 15 '12 at 23:47

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

Switched branches and reset db in other branch, forgot to migrate in this one. Thanks! :) — Mosselman, Sep 11 '14 at 12:36

ExiRe · Answer 2 · 2012-09-29T14:24:01.120

6

I suppose that author just forgot to run:

rake db:migrate

ALso, if you met such error inside of your tests then you should run:

rake db:test:prepare

edited Sep 29 '12 at 14:24

answered Sep 25 '12 at 14:04

ExiRe

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Arel · Answer 3 · 2017-10-07T03:18:51.180

6

Also, for anyone getting this error on heroku, you need to run

heroku run rake db:migrate

and

heroku restart

in the terminal after adding/removing fields/tables from your database.

edited Oct 07 '17 at 03:18

answered Jun 28 '13 at 20:37

Arel

3,888
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saved the day. Thank you! – beydogan Nov 24 '16 at 19:10

score 0 · Answer 4 · answered Jul 10 '13 at 12:25

Kreek, this is obviously a minor oversight, as most people would have realized by now, you probably meant to run this command, as one should, outside the console, otherwise, one would get the following:

'NameError: undefined local variable or method `migrate' for main:Object'.

score 0 · Answer 5 · answered Jul 07 '19 at 11:21

I had similar problem but mine was because I was copying and pasting codes and forgot to delete

mount_uploader :picture, PictureUploader

from my model which did not use pictures. Hope this help others in future who could not figure out what happened

carrierwave - rails 3.1- undefined method: image_will_change

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