collection_select not saving selected option in database

Question

I have collection_select in one of my views, which properly creates a HTML <select> menu, but when I select an option it does not save in the database. In the same view I have other fields from the same db table and they save up. Here are my models:

class TrainingPart < ActiveRecord::Base
  belongs_to :activity
  belongs_to :training  
  accepts_nested_attributes_for :activity, :allow_destroy => true
end

class Activity < ActiveRecord::Base
  has_many :training_parts 
end

The partial is:

<div class="part">
  <%= f.label :activity, "Activity" %>
  <%= collection_select :training_part, :activity_id, Activity.all, :id, :name %>
  <%= f.text_field :activity_id %>
  <%= f.text_field :amount %>  
</div>

The amount field works fine.

EDIT: I don't use attr_accessible in any model, so all of the fields in all tables are accessible. (reference: Rails mass assignment definition and attr_accessible use)

Do you have `attr_accessible :activity_id` in your `TrainingPart` model? — Substantial, Feb 16 '12 at 11:16
no, and when I added it there was the following error: `Can't mass-assign protected attributes: amount` — maya, Feb 16 '12 at 11:26

score 1 · Accepted Answer · answered Feb 16 '12 at 19:22

I managed to do it. It turned out that I had 2 mistakes:

1) I had to remove <%= f.text_field :activity_id %> from the view as this was the field, which I was trying to set with the select menu.

2) I should've used f.collection_select instead of collection_select

Dennis · Answer 2 · 2014-03-03T20:35:39.307

For me the problem was that I didn't whitelist the field in my controller.

Say your select menu has blog posts as options so you can choose what blog a comment belongs to

f.collection_select :post_id, Post.all, :id, :name

Then you'll need to permit post_id in your CommentsController

def update
  # ...
  if @comment.update_attributes(post_params)
  # ...
end

def post_params
  params.require(:comment).permit(:name, :post_id)  # Make sure the field used with your select menu is permitted! 
end

score 0 · Answer 3 · answered Feb 16 '12 at 11:33

Allow mass-assignment to whatever attributes you want settable from the view:

attr_accessible :activity_id, :amount # ...any others...

"Mass-assignment" means setting many attributes at once with data from the view, such as from forms. These attributes are protected by default to prevent users from injecting their own values (eg. admin = true).

Use attr_accessible to declare which of your model's attributes are mass-assignable.

Also, since you are accepting nested attributes for Activity, you must include :activity_attributes among your list of accessible attributes.

collection_select not saving selected option in database

3 Answers3