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Creating Instance of Nested model inside parent controller

January 18Hits:1

I would like to know if it is possible to create an instance of a nested model inside the parents controller.

Let me explain. I have a model called Museum and another model called Museumimage. Museumimage has only one field which is an attachment, managed by the Paperclip gem. I have created a separate model for this because there can be as many images as desired linked to the Museum model. I thought this would be better than creating, lets say, 20 attachment fields for the Museum model... Most of it being empty..

Then in the NEW view, I have a form allowing to both adding the information for the Museum instance and somes file fields too.

Here is my view important bits :

<%= form_for :museum, url: museums_path do |f| %> <p>   <%= f.label :name %><br>   <%= f.text_field :name %>    </p> .... <%= f.file_field :image %><br> 

(some params such as :name belongs to the Museum model, and :image to the second nested model Museumimage)

I did a pretty straightforward controller, with the CREATE important bits being :

@museum = Museum.new(museum_params) @museum.save @image = @museum.museumimages.create(image_params) redirect_to @museum 

(for one image at the moment)

Though I get error : ActionController::ParameterMissing in MuseumsController#create

This is my first attempt at Paperclip as well.

My questions :

  • Is it possible to create an instance on a nested model inside parents controller ?
  • if this is possible I guess my code has flaws. Intuitively I think my form helper should make a reference to the nested model :museumimage too ?


I have found a beginning of a solution with the form helpers FIELDS_FOR.

<%= f.fields_for :museumimages do |museumimages_fields| %>   Image: <%= museumimages_fields.file_field :image %>     <% end  %> 

But I still get the error message param is missing or the value is empty: museumimages

app/controllers/museums_controller.rb:191:in `image_params' app/controllers/museums_controller.rb:129:in `create'  "museumimages"=>{"image"=>#<ActionDispatch::Http::UploadedFile:[email protected]=#<Tempfile:C:/Users/Maxence/AppData/Local/Temp/RackMultipart20160118-8768-obyvra.JPG>, @original_filename="DSC07825.JPG", @content_type="image/jpeg", @headers="Content-Disposition: form-data; name=\"museum[museumimages][image]\"; filename=\"DSC07825.JPG\"\r\nContent-Type: image/jpeg\r\n">}}, 

I think my controller bits are not correct.

Def Create  ... @image = @museum.museumimages.new(image_params) @image.save end  def image_params params.require(:museumimages).permit(:image) end 


You need to take a look to accept nested attributes method, this way the model will allow the instance to be saved, then in the method image_params you will need to add an extra param in array form, in this case params.require(:museum).permit(:name, museumimages: [:image])

and that should do the trick

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