If you want to add many attachments to a record using just a file field, but you don’t want to remove the previous images from the record on every update, like in the following code:

<%= form_with(model: product) do |form| %>
    <%= form.label :images %>
    <%= form.file_field :images, multiple: true %>
  <%= form.submit %>
<% end %>

And instead, on every update you want to add the new images to the record, here is a simple workaround…

A virtual new_images attribute

Instead of using the :images attribute, you can add a virtual :new_images attribute, using an attr_reader and a custom writer like this:

class Product < ApplicationRecord
  attr_reader :new_images

  has_many_attached :images

  def new_images=(images)
    self.images.attach(images)
  end
end

And use that attribute in your file_field:

<%= form_with(model: product) do |form| %>
    <%= form.label :new_images %>
    <%= form.file_field :new_images, multiple: true %>
  <%= form.submit %>
<% end %>

Also, update your “params method” in the controller:

def create
  @product = @site.products.new(product_params)
  #...
end

def update
  @product.update(product_params)
  # ...
end

private

def product_params
  params.require(:product).permit(new_images: [])
end

This way, when you assign new images, your record will attach the received images instead of updating the images field with the new images.

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