rails 4 simple_form belongs_to association undefined method error

Question

Using rails 4, when I want to render a form (with simple_form) from an object Document::Document I have this error: undefined method document_type_id for #<Document::Document:0x007fada4a50240>

Here a part of my model:

class Document::Document < ActiveRecord::Base
   ...
   belongs_to :document_type, -> {include(:translations)}, :class_name => 'Document::Type'
   ...
end

The method new of my controller:

def new
   @document = Document::Document.new
end

And a part of the form with simple_form:

=f.association :document_type, prompt: t('document.documents.form.choose_document_type'), collection: Document::Type.includes(:translations)

The error:

undefined method `document_type_id' for #<Document::Document:0x007fada4a50240>
Extracted source (around line #14):

   11    .row
   12      =f.input :language, collection: languages_list, prompt: t("document.documents.form.choose_language"), label_html: tooltip(t('document.documents.forms.tooltips.language')), wrapper_html: {class: 'columns large-4'}, input_html: {class: 's2'}
   13      =f.input :study_level, prompt: t('document.documents.form.choose_study_level'), label_html: tooltip(t('document.documents.forms.tooltips.study_level')), wrapper_html: {class: 'columns large-4'}, input_html: {class: 's2'}
   14      =f.association :document_type, prompt: t('document.documents.form.choose_document_type'), collection: Document::Type.includes(:translations), label_html: tooltip(t('document.documents.forms.tooltips.type')), wrapper_html: {class: 'columns large-4'}, input_html: {class: 's2'}
   15      -#=f.association :domains, collection: Domain.includes(:translations).order('name ASC'), label_html: tooltip(t('document.documents.forms.tooltips.domains')), input_html: {class: 's2'}
   16    .form-actions
   17       =f.button :submit, t('document.documents.form.submit') 

Why this error ?

I upgraded from rails 3.2. Before everything works great.

In rails 3.2 I had added that:

attr_accessible :document_type_id, ...

Maybe the error is coming from there

Answer 1

Sorry for the inconvenient.

It was an issue with migration. Someone else changed the migration file and the field document_type_id was no more present in the table of the database.

It took me a while until I find this stupid issue.

Thanks for the reply and apologise

Answer 2

Check the version of the simple_form Gem. Should be >= 3.0.0 Not sure how the simple_form gem works, but rails 4 doesn't use attr_accessible anymore (still, you can install the gem, but it's likely to be deprecated soon)

Rails 4 now uses Strong Parameters. Basically works like this: you define in a private method in the controller which parameters are whitelisted to be used, so if your document_type_id is not in the list it is ignored.

Rails 4 scaffold generator automatically adds this method and accepts all params by default if you want to see what it looks like.

Hope it helps!