Rails how to build on iteration

After trying to save a set of images with dropzone without iteration. i switch to iterating the images and try to save on the loop. but rails spitting

ActiveRecord::StatementInvalid at /products =========================================== > SQLite3::ConstraintException: NOT NULL constraint failed: images.product_id: INSERT INTO "images" ("created_at", "ifoto", "product_data_id", "product_id", "updated_at") VALUES (?, ?, ?, ?, ?) app/controllers/products_controller.rb, line 214 ------------------------------------------------ ruby 209 210 if params[:images] && params[:images][:ifoto] 211 params[:images][:ifoto].values.each do |ifoto| 212 213 @image.ifoto = ifoto > 214 @image.save 215 216 217 end 218 render :nothing => true 219 App backtrace ------------- - app/controllers/products_controller.rb:214:in block (3 levels) in create' - app/controllers/products_controller.rb:211:inblock (2 levels) in create' - app/controllers/products_controller.rb:137:in `create' Full backtrace --

here is the dropzone code

 format.json do
     @product = current_vitrine.products.build(params[:product])
        @image =  @product.images.build(params[:images])



if params[:images] && params[:images][:ifoto]
       params[:images][:ifoto].values.each do |ifoto|

@image.ifoto = ifoto
  @image.save


                    end
    render :nothing => true

    end
  end

someone have a hint to this kind of problem?