通过 Paperclip 上传图像而不保存对象

Question

I'm working in Rails and I have two models, a prelaunch and an initiative. Basically I want a user to be able to create an initiative using the attributes of the prelaunch. Basically what I want to have happen is when a user visit's their prelaunch and is ready to turn it into an initiative, it brings them to a form that has their prelaunch information already populated and they can just add the additional info. I've managed to do this for every attribute so far except for the attached image, called :cover_image.

I think the problem is that I'm setting the initiative's cover_image to the prelaunch's cover_image on the new action of my controller, but because this is the new action and not create, I'm not saving the initiative yet. I think this means the cover_image isn't getting reuploaded yet, so @iniative.cover_image.url doesn't point to anything. It also doesn't appear to be prepopulating the file field of my form with anything.

I'm not entirely sure how feasible all of this is, but it's what the client asked for so I'm trying to make it work for them.

Here's my controller:

def new
  @initiative = Initiative.new
  populate_defaults(@initiative)
  @initiative.build_location
  3.times{ @initiative.rewards.build }
  @initiative.user = current_user
  if !params[:prelaunch_id].nil? && !params[:prelaunch_id].empty?
    # if user is transferring a prelaunch, assign its attributes to the intiative
    @prelaunch = Prelaunch.find(params[:prelaunch_id])
    @initiative.assign_attributes(title: @prelaunch.title,
                                teaser: @prelaunch.teaser,
                                category: @prelaunch.category,
                                funding_goal: @prelaunch.funding_goal,
                                term: @prelaunch.campaign.term,
                                story: @prelaunch.story,
                                location: @prelaunch.campaign.location,
                                video_url: @prelaunch.video_url,
                                EIN: @prelaunch.campaign.EIN,
                                nonprofit: @prelaunch.nonprofit,
                                organization_name: @prelaunch.campaign.organization.name)
  end
end

Edit:

Thanks to peterept's answer below I've managed to get the prelaunch cover_image into the form and into the create action of the initiatives controller. The problem now is that everything seems to work perfectly in the create action: the initiative gets the prelaunch's cover image, it saves without error, and it redirects to the show action.

UNFORTUNATELY, By the time it reaches the show action of the controller, @initiative.cover_image is set to the default again. I can't figure out what could possibly be happening between the successful create action and the show action.

Here are the create and show actions of the initiatives controller:

  def create
    if !params[:initiative][:prelaunch_id].nil? && !params[:initiative][:prelaunch_id].empty?
      @prelaunch = Prelaunch.find(params[:initiative][:prelaunch_id]) # find the prelaunch if it exists
    end
    @initiative = Initiative.new(initiatives_params)
    @initiative.user = current_user
    begin
      @payment_processor.create_account(@initiative)
      if @initiative.save
        # @prelaunch.destroy # destroy the prelaunch now that the user has created an initiative
        flash[:alert] = "Your initiative will not be submitted until you review the initiative and then press 'Go Live' on the initiative page"
        redirect_to initiative_path(@initiative)
      else
        flash[:alert] = "Initiative could not be saved: " + @initiative.errors.messages.to_s
        render :new
      end
    rescue Exception => e
      logger.error e.message
      flash[:error] = "Unable to process request - #{e.message}"
      render :new
    end
  end

  def show
    @initiative = Initiative.find(params[:id])
    @other_initiatives = Initiative.approved.limit(3)
  end

And here is the initiatives_params method from the same controller:

def initiatives_params
  initiative_params = params.require(:initiative).permit(
    :terms_accepted,
    :title,
    :teaser,
    :term,
    :category,
    :funding_goal,
    :funding_type,
    :video_url,
    :story,
    :cover_image,
    :nonprofit,
    :EIN,
    :role,
    :send_receipt,
    :organization_name,
    :crop_x, :crop_y, :crop_h, :crop_w,
    location_attributes: [:address],
    rewards_attributes: [:id, :name, :description, :donation, :arrival_time, :availability, :_destroy, :estimated_value])
  if @prelaunch.media.cover_image
    initiative_params[:cover_image] = @prelaunch.media.cover_image
  end
  initiative_params
end

Answer 1

You can pass the Image URL and display it on the page.

The user can then override this by uploading a new image (as per normal).

In you're create action, if they have not supplied a new image, then set it to the one in the assocoiated prelaunch - you'd want to copy the original so it doesn't get replaced if they upload a new one. (If you don't know which was the prelaunch, you could pass the ID down to the page).

Answer 2

I was able to make it work by saving the Paperclip object only. This is my model:

class Grade < ActiveRecord::Base
  has_attached_file :certificate
end

If I run the following:

@grade.certificate = new_file
@grade.certificate.save

It saves/overwrite the file, but don't update the Grade object.

Versions: ruby-2.3.8 , Rails 4.2.11.3 and paperclip (4.3.6)