Saving generated Image with Carrierwave - no form, all inside the model

this is a tricky one, I hope someone can help me.

I have a article_set, which has many set_items, each set item has an image. I want to create an collage of the images, so one image out of many, and save it with carrierwave.

that's whats going on in my model:

require 'RMagick'

class ArticleSet < ActiveRecord::Base

    # ...

    after_create :create_collage  
    mount_uploader :blog_image, BlogImageUploader

    def create_collage
      # load the template
      template = Magick::Image.read("#{RAILS_ROOT}/public/images/set_template.png").first

      # go through all set items by z_index and add lay it over the template
      for item in self.set_items
        photo = Magick::Image.read(item.product.assets.first.image.url(:thumb).to_s).first
        photo.scale(item.width, item.height)
        # composite item over template offsetting pos_x and pos_y for the template border
        template.composite!(photo, item.pos_x, item.pos_y, Magick::OverCompositeOp)
      end

      # save composite image to JPG
      template.write("set_#{self.id}_#{开发者_JAVA百科Time.now.to_i}.jpg")

      #save and upload to s3

      self.blog_image.store!(template)
      self.blog_image = self.blog_image.store_path
      self.write_carrierwave_identifier
      self.save  

    end

end

So far, so good. I can save the set and it runs though this method, but I guess the last part

       #save and upload to s3

      self.blog_image.store!(template)
      self.blog_image = self.blog_image.store_path
      self.write_carrierwave_identifier
      self.save  

is probably incorrect, in my database I get only NULL values for blog_image. It should, of course, contain the file name of the generated file... any help highly appreciated.

thanks

That 3rd last line looks a bit dodgy:

self.blog_image = self.blog_image.store_path

If you remove that i'm fairly sure it should work.