add compare method after update method executed

photo_galleries_controller.rb

def update
    respond_to do |format|
      if @photo_gallery.update(photo_gallery_params)
         # add compare method in here
        compare_photos(params[:photos])
        format.html { redirect_to @photo_gallery, notice: 'Photo gallery was successfully updated.' }
        format.json { render :show, status: :ok, location: @photo_gallery }
      else
        format.html { render :edit }
        format.json { render json: @photo_gallery.errors, status: :unprocessable_entity }
      end
    end
  end