Rename image using associated model - Paperclip - ruby-on-rails

Question

Code
In my image model:
has_attached_file :pic
before_post_process :rename_pic
before_save ->{ p 'before_save ----------------' }
after_post_process ->{ p 'after_post_process --------------' }
def rename_pic
p 'en imagen'
p self
p 'en imagen'
end
In service that has many images:
# don't use accepts_nested_attributes_for
before_save :create_images
attr_accessor :images_attributes
def create_images
# images_attributes example value: { "0"=> {img_attrs}, "1" => {img_attrs1} }
images_attributes.all? do |k, image_attrs|
if image_attrs.delete(:_destroy) == "false"
p 'asd'
image = Image.new image_attrs.merge(service_id: id)
p image.service
p image.service_id
image.save
end
end
end
This is the output I get:
"asd"
"en imagen"
#<Image id: nil, service_id: nil, pic_file_name: "Screen_Shot_2013-04-07_at_5.18.03_PM.png", pic_content_type: "image/png", pic_file_size: 16041, pic_updated_at: "2013-07-30 22:58:46", created_at: nil, updated_at: nil, user_id: nil>
"en imagen"
G"after_post_process --------------"
#<Service id: 427, event_id: nil, min_capacity: nil, max_capacity: nil, price: #<BigDecimal:7fb6e9d73d48,'0.0',9(18)>, image_path: nil, name: "Super Franks", desc: "zxc", created_at: "2013-05-12 19:01:54", updated_at: "2013-07-30 19:32:48", address: "pasadena", longitude: 77.225, latitude: 28.6353, gmaps: true, city: "san francisco", state: "california", country_id: "472", tags: "Banquet", created_by: 22, avg_rating: #<BigDecimal:7fb6efdbcf10,'0.0',9(18)>, views: 27, zip_code: "", address2: "", price_unit: "", category_id: 3, featured: true, publish: true, slug: "banquet-super-franks", discount: nil, currency_code: "USD", video_url: "http://www.youtube.com/watch?v=A3pIrBZQJvE", short_description: "">
427
"before_save ----------------"
Problem
When calling
image = Image.new image_attrs.merge(service_id: id)
Paperclips seems to start processing, and then set service_id.
So when I try to use service inside rename_pic service is nil.
Any ideas on how to handle this?

Answer 1

This solved my problem, I changed:
before_post_process :rename_pic
to:
before_create :rename_pic
and this is rename_pic, for the record:
def rename_pic
extension = File.extname(pic_file_name).downcase
self.pic.instance_write :file_name,
"#{service.hyphenated_for_seo}#{extension}"
end
where service has_many images, and image belongs_to service.

Answer 2

Be carefull with the fix of #juanpastas, because if you change before_post_process to before_create, it will only run when you create your image, and not when you update it. To have the callback still run on update, do this:
class YourImage
has_attached_file :pic
# use both callbacks
before_create :rename_pic
before_post_process :rename_pic
def rename_pic
# assotiated_object is the association used to get pic_file_name
return if self.assotiated_object.nil?
extension = File.extname(pic_file_name).downcase
self.pic.instance_write :file_name,
"#{service.hyphenated_for_seo}#{extension}"
end
end