Rails Paperclip how to delete attachment?

I am using Paperclip (w/ Amazon s3) on Rails 3. I want to delete an existing attachment without replacing it using an update action.

I've only found one example of this here and could not get that to work, it just wouldn't delete and there was nothing in the logs to say why. I wanted to do something like this on the form:

<%- unless @page.new_record? || [email protected]? -%>
    <%= f.check_box :image_delete, :label => 'Delete Image' %>
<%- end -%>

(page is the name of the model, image is the attribute name which holds the attachment)

But how do I detect that checkbox and more importantly, how do I delete the image? I appreciate any help!

First off, when you create a check_box in a form_for (which it looks like you are), then the form should by default send :image_delete as "1" if checked and "0" if unchecked. The method declaration looks like this:

def check_box(method, options = {}, checked_value = "1", unchecked_value = "0")

Which shows that you can assign other values if you want to, but that is of course optional.

Secondly, the call to manually delete an attachment without deleting the model instance to which it is attached to is:

@page.image.destroy #Will remove the attachment and save the model
@page.image.clear #Will queue the attachment to be deleted

And to accomplish your way of deleting the images through a checkbox, perhaps add something like this to your Page model:

class Page < ActiveRecord::Base
  has_attached_file :image

  before_save :destroy_image?

  def image_delete
    @image_delete ||= "0"
  end

  def image_delete=(value)
    @image_delete = value
  end

private
  def destroy_image?
    self.image.clear if @image_delete == "1"
  end
end

This way, when you create your form and add the :image_delete checkbox, it will load the default value "0" from the User instance. And if that field is checked then the controller will update the image_delete to "1" and when the User is saved, it will check if the image is to be deleted.

has_attached_file :asset

=>

    attr_accessor :delete_asset
    before_validation { asset.clear if delete_asset == '1' }

No need to destroy asset, Paperclip will do it.

In the form form.check_box(:delete_asset) will suffice.

This is Benoit's answer, but wrapped in a module, and covering the edge case of nested attribute models where the destroy tickbox is the only thing changed on the model.

It will apply to all attachments on the model.

# This needs to be included after all has_attached_file statements in a class
module DeletableAttachment
  extend ActiveSupport::Concern

  included do
    attachment_definitions.keys.each do |name|

      attr_accessor :"delete_#{name}"

      before_validation { send(name).clear if send("delete_#{name}") == '1' }

      define_method :"delete_#{name}=" do |value|
        instance_variable_set :"@delete_#{name}", value
        send("#{name}_file_name_will_change!")
      end

    end
  end

end

remember to add this to your Page model too:

attr_accessible :image_delete

Modified version of Paul's solution, to support Rails 5 custom attributes. I just wish there were a way to include the module at the top of the file, before has_attached_file definitions.

module Mixins
  module PaperclipRemover

    extend ActiveSupport::Concern

    included do
      attachment_definitions.keys.each do |name|

        attribute :"remove_#{name}", :boolean

        before_validation do
          self.send("#{name}=", nil) if send("remove_#{name}?")
        end

      end
    end

  end

end

Was able to achieve this with less code, by just implementing a delete_attachment on the model's side.:

class MyModel < ApplicationRecord
  has_attached_file :image

  def image_delete=(other)
    self.image = nil if other == "1" or other == true
  end
end