Models with attachments and one AttachmentsController: how?

rubyonrails-talk
1

First off, I beg your pardon for the somewhat cryptic topic, but I couln't think of anything better.

The issue I'm facing is that I have some models (User, Product, Maker) which can have one or more attachments:

A User has_one avatar A Maker has_one logo A Product has_many pictures, and has_many documents

"Avatar", "logo" and "documents" are all aliases for a model named "Attachment" and, thus, the aforementioned relations are all polymorphic.

I'm using "attachment_fu" plugin to handle attachments.

While writing the code I've found that there are many such constructs repeating all over:

  def update     flash[:error] = "couldn't update product" unless @product.update_attributes(params[:product])     if !params[:attachment].blank?       flash[:error] = "couldn't add the attachment" unless @product.attachments << Attachment.create(params[:attachment])     end     redirect_to edit_product_path(@product)   end

This smells a lot. I thought there should be one controller in charge of handling attachments, namely AttachmentsController, so far so good.

But...since the AttachmentsController would be "REST style", it will only have one "create" action which will be used in different contexts (User, Product, Maker). Create action will be passed the usual "params" hash built like this: :xxxxx_id => 1, :uploaded_data => "...."

Where "xxxxx_id" will be replaced by "user_id", "product_id" and "maker_id" depending on the what model I'm creating attachment for.

Being params: :user_id => 1, :uploaded_data => "some stuff"

I thought the AttachmentsController#create action should look like:

context = params.keys.find do |k| k.to_s =~ /.*_id/ end class_type = eval(context.to_s.gsub(/.*_id/,'').classify) instance = class_type.find(params[context]) instance.attachments.create(params[:uploaded_data])

Is that a correct way to proceed, or there's an easier and cleaner way?

Thanks in advance for your help

Regards, Carmine

2

what you're describing is a polymorphic association. http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#M000980

3

Hi Jeff,

Jeff Emminger wrote:

what you're describing is a polymorphic association. ActiveRecord::Associations::ClassMethods

Indeed, Attachment is associated polymorphically to the other models.

What I want to accomplish is removing code duplication from some of the controllers. Let's say I have:

- User has_one :attachment, :as => :attachable - Maker has_one :attachment, :as => :attachable - Product has_many :attachments, :as => :attachable

Now, in their respective controllers, the "update" action looks like this:

def update     flash[:error] = "couldn't update product" unless @product.update_attributes(params[:product])     if !params[:attachment].blank?       flash[:error] = "couldn't add the attachment" unless @product.attachments << Attachment.create(params[:attachment])     end     redirect_to edit_product_path(@product)   end

The "interesting" part is the one where the Attachment gets created and associated to its "owner" (in that case, the Product).

This part is repeated also in the UsersController and MakersController.

I thought that, trying to comply to the "everything is a resource" mantra, I should move that part outside the afore mentioned controllers and in a controller of its own. Say: AttachmentsController.

Routes are set as follows:

map.resources :users do |user|   user.resource :attachment, :controller => 'attachments' end

map.resources :makers do |maker|   maker.resource :attachment, :controller => 'attachments' end

map.resources :products do |product|   product.resources :attachments, :controller => 'attachments' end

This leads to a problem. User, maker and products "edit" view will have to use AttachmentsController in order to create a new attachment for their respective model. Hence, they will all call AttachmentsController#create action passing parameters.

To solve this problem, I thought of implementing the "create" action that way:

context = params.keys.find do |k| k.to_s =~ /.*_id/ end class_type = eval(context.to_s.gsub(/.*_id/,'').classify) instance = class_type.find(params[context]) instance.attachments.create(params[:uploaded_data])

And the question is: is it correct to have AttachmentsController handle the attachments of user, maker and product models, or should I stick with the shown "update" action and let UsersController, MakersController and ProductsController handle the attachments?

Now, I beg your pardon if I've been unclear (my english is worse than my code :slight_smile: ).

Thanks for your help

4

And the question is: is it correct to have AttachmentsController handle the attachments of user, maker and product models, or should I stick with the shown "update" action and let UsersController, MakersController and ProductsController handle the attachments?

It's correct in my opinion... you have only one place to maintain the attachment code.