Active Admin Rails 4 has many

Question

I am working with Rails 4, Active Admin and Paperclip to setup a has_many images association. When generating my has_many portion of the form I keep getting errors. Currently I am getting undefined method `+' for nil:NilClass. Here is my code:

news model

class News < ActiveRecord::Base
    validates :body, presence: true
    validates :title, presence: true, length: { maximum: 140 }

    has_many :news_images, dependent: :destroy
end

News image model

class NewsImage < ActiveRecord::Base
    belongs_to :news



    has_attached_file :photo, styles: {
        small: "150x150>",
        medium: "300x300>",
        large: "600x600>"
    }
    validates_attachment_presence :photo
    validates_attachment_size :photo, less_than: 5.megabytes
end

admin code

ActiveAdmin.register News do
    index do
    column :title
    default_actions
  end

  form multipart: true do |f|
    f.semantic_errors *f.object.errors.keys

    f.inputs "News Details" do
      f.input :title
      f.input :body, :as => :rich
    end

    f.has_many :news_images do |p|

    end

    f.actions
  end

  controller do
    def permitted_params
      params.permit news: [:title, :body, news_images: [:photo]]
    end
  end
end

Ideally I would like the user to be able to upload multiple images to the form. Any one have experience with this issue?

The stack trace is saying insert_tag renderer_for(:new) which is being tripped on f.has_many :news_images do |p|

Answer 1

So the problem was with the news model. I thought accepts_nested_attributes_for was deprecated with the addition of strong params but I guess I was wrong adding this to the news model fixed my issue

accepts_nested_attributes_for :news_images,
                            :reject_if => lambda { |attributes| attributes[:photo].blank? },
                            :allow_destroy => true

Answer 2

There was another bug in Paperclip 4.1 that was fixed recently: https://github.com/thoughtbot/paperclip/issues/1457

I spent a ton of time tracking this down, but finally was able to find the connection between formtastic and paperclip 4.1.

The solution that worked for me was to switch to paperclip's master branch in my Gemfile as follows:

gem 'paperclip', github: 'thoughtbot/paperclip'