Rails admin and has_and_belongs_to_many

Question

I am using the Rails Admin gem. And I have the following two models:

class Category < ActiveRecord::Base
  attr_accessible :description, :name

  has_and_belongs_to_many :experiences
end


class Experience < ActiveRecord::Base
  attr_accessible :description, :city_id, :price, :title, :user_id
  attr_accessible :categories

  validates :title, :description, :user_id, :presence => true

  belongs_to :user
  belongs_to :city
  has_and_belongs_to_many :categories
end

In the Rails admin, I am not able to add a category to an existing Experience. In the edit site of a particular Experience, I see this:

As you can see I can't select any categories, even though I have several categories created.

Answer 1

It was solved by adding the following into the Experience model:

attr_accessible :category_ids

instead of

attr_accessible :categories