How do you delete images in ActiveAdmin form?

Question

I currently have a HABTM relationship between art and art_pic_attachment (which are images). No problem in creating objects but when I want to delete an image - I can't find any clean documentation that shows how to delete an image. I've tried the _destroy option but nothing happens. Any clue how to fix this?

ActiveAdmin.register Art do

permit_params :art_pic_attachments_attributes: [:id, :picture, :_destroy]

 form(html: { multipart: true }) do |f|
    f.inputs do

        f.has_many :art_pic_attachments, allow_destroy: true, heading: 'Images' do |ff|
            ff.file_field :picture, required: true, heading: "Pictures"
        end

    end
        f.actions
 end 

Model:

class Art < ApplicationRecord
        has_many :art_pic_attachments, dependent: :destroy
        accepts_nested_attributes_for :art_pic_attachments, allow_destroy: true  
    end

Answer 1

This wiki article discusses how to do this with Paperclip and overriding <attachment_name>_attributes=, eg.

def attachment_attributes=(attributes)
  attachment.clear if has_destroy_flag?(attributes) && !attachment.dirty?
end