Class variable in Concern Rails 4 -

i created concern encapsulate logic upload images resources of application, let's example there's image associated each course, , same every user.

module picturable     extend activesupport::concern     included       path_image = file.join rails.root,"public","#{table_name}_imgs"       after_save :save_image     end   def photo=(file)     unless file.blank?       @file = file       self.extension = file.original_filename.split(".").last.downcase     end   end   def path_image     file.join path_image, "#{self.id}.#{self.extension}"   end   def path_img     "/#{self.class.table_name}_imgs/#{self.id}.#{self.extension}"   end    def has_image?     file.exists? path_image   end    private   def save_image     unless @file.nil?         fileutils.mkdir_p path_image          file.open(path_image, "wb") |f|              f.write(@file.read)         end         @file =nil     end   end end 

i have edited code because of methods in spanish, concern works expected problem table_name variable, haven't been able understand how value changes, gets value of users, value of courses, of course errors because framework search image of users in folder of courses , vice versa.

the way i'm including concern looks follow:

class course < activerecord::base   include picturable end 

i want include concern in each model going have in image associated, need save images in different folders representing each 1 of resources, let's users images should saved in users_imgs folder, , courses's images should saved in courses_imgs , on.

any clue in doing wrong or if approach wrong one.

here error explained rails console:

thanks

the problem constant within included block being overwritten. can around using method instead of constant. here's example i've defined method called image_root_path replaces constant.

module picturable   extend activesupport::concern   included     after_save :save_image   end    def image_root_path     file.join rails.root,"public","#{self.class.table_name}_imgs"   end    def path_image     file.join image_root_path, "#{self.id}.#{self.extension}"   end    # ...    private   def save_image     unless @file.nil?       fileutils.mkdir_p image_root_path        file.open(path_image, "wb") |f|          f.write(@file.read)       end       @file =nil     end   end end