rails-gems-blog-snippet-9.rb

# Offer model code
has_and_belongs_to_many :offer_attachments, join_table: "oa_join"
has_many :offer_random_attachments, :dependent => :destroy

class OfferAttachment < ActiveRecord::Base
    has_and_belongs_to_many :offers, join_table: "oa_join"
end

class OfferRandomAttachment < ActiveRecord::Base
    belongs_to :offer
    has_attached_file :random_attachment, :path => ":rails_root/storage/docs/offers/random_attachments/:id/:filename", :url => "/storage/docs/offes/random_attachments/:id/:filename"

    do_not_validate_attachment_file_type :random_attachment
end

# View code
# first use case
<div class="field">
    <%= f.label "Attachment to be sent" %><br>
    <%= f.collection_check_boxes :offer_attachment_ids, OfferAttachment.all, :id, :name do |b| %>
        <div class="collection-check-box">
            <%= b.check_box %>
            <%= b.label %>
        </div>
    <% end %>
</div>


# second use case
<div class="control-group">
    <%= f.label :offer_random_attachments, :class => 'control-label' %>
    <div class="controls">
        <%= file_field_tag "random_attachments[]", type: :file, multiple: true %>
    </div>
</div>