Deleting a Paperclip Attachment in Activeadmin - ruby-on-rails

Question

I'm using paperclip to add image attachments to several models and Activeadmin to provide a simple admin interface.
I have this code in my activeadmin model file which allows for image uploads:
form :html => { :enctype => "multipart/form-data"} do |f|
f.inputs "Details" do
f.input :name
f.input :subdomain
end
f.inputs "General Customisation" do
f.input :standalone_background, :hint => (("current image:<br/>").html_safe + f.template.image_tag(f.object.standalone_background.url(:thumb))).html_safe, :as => :file
end
end
which works fine. All of the images I'm attaching like this are optional and so I'd like to give the user the option to remove a previously added image but can't work out how to do this in Activeadmin. All of the example I've seen are for situations where the attachments are managed through a separate has_many association rather than being part of the main model.
Does anyone know of a way to do this?

Answer 1

In your active admin view
form :html => { :enctype => "multipart/form-data"} do |f|
f.inputs "Details" do
f.input :name
f.input :subdomain
end
f.inputs "General Customisation" do
f.input :standalone_background, :hint => (("current image:<br/>").html_safe + f.template.image_tag(f.object.standalone_background.url(:thumb))).html_safe, :as => :file
f.input :remove_standalone_background, as: :boolean, required: false, label: "remove standalone background"
end
end
In your model
You could define a status flag like bellow
attr_writer :remove_standalone_background
def remove_standalone_background
#remove_standalone_background || false
end
OR (depreciated in rails 3.2)
attr_accessor_with_default : standalone_background,false
before_save :before_save_callback
And
def before_save_callback
if self.remove_standalone_background
self.remove_standalone_background=nil
end
end

Answer 2

You could implement this by creating a custom method. This can be done
member_action :custom_action, :method => :get do
//code
end
Also you should add a custom column with a link such as
index do
column "Custom" do |item|
link_to "Custom action", "/admin/items/custom_action"
end
end

Answer 3

Another option is to have a status flag for the attachment or image. Before saving the edited object, you unlink the image.

Answer 4

Thank you for your help guys. This is the final working code...
admin/product.rb
f.input :image, required: false, hint: (("Current image:<br/>").html_safe + f.template.image_tag(f.object.image.url(:thumb))).html_safe
f.input :remove_image, as: :boolean, required: false, label: "Remove Image"
models/product.rb
attr_writer :remove_image
def remove_image
#remove_image || false
end
before_validation { self.image.clear if self.remove_image == '1' }

Answer 5

Although accepts_nested_attributes_for(:foo, allow_destroy: true) only works with ActiveRecord associations like belongs_to we can borrow from its design to have paperclip attachment deletion work in a similar way.
(To understand how nested attributes work in Rails see http://api.rubyonrails.org/classes/ActiveRecord/NestedAttributes/ClassMethods.html).
Add a <attachment_name>_attributes= writer method like below to your model that already uses has_attached_file:
has_attached_file :standalone_background
def standalone_background_attributes=(attributes)
# Marks the attachment for destruction on next save,
# if the attributes hash contains a _destroy flag
# and a new file was not uploaded at the same time:
if has_destroy_flag?(attributes) && !standalone_background.dirty?
standalone_background.clear
end
end
The <attachment_name>_attributes= method calls Paperclip::Attachment#clear to mark the attachment for destruction when the model is next saved.
Next open the existing app/admin/your_model_here.rb file (use the correct file path for your app) and setup strong parameters to permit the _destroy flag nested attribute on <attachment_name>_attributes:
ActiveAdmin.register YourModelHere do
permit_params :name, :subdomain,
:standalone_background,
standalone_background_attributes: [:_destroy]
In the same file, add a nested _destroy checkbox to the ActiveAdmin form block. This checkbox must be nested within <attachment_name>_attributes using semantic_fields_for (or one of the other nested attributes methods provided by formtastic).
form :html => { :enctype => "multipart/form-data"} do |f|
f.inputs "Details" do
...
end
f.inputs "General Customisation" do
...
if f.object.standalone_background.present?
f.semantic_fields_for :standalone_background_attributes do |fields|
fields.input :_destroy, as: :boolean, label: 'Delete?'
end
end
end
end
Your form should now show a delete checkbox when there is an attachment present. Checking this checkbox and submitting a valid form ought to delete the attachment.
Source: https://github.com/activeadmin/activeadmin/wiki/Deleting-Paperclip-Attachments-with-ActiveAdmin