ruby - Dynamically including a Rails Concern -

my objective dynamically load set of methods activerecord model instance based on attribute that's set:

class book < activerecord::base   after_initialize |cp|     self.class.include "#{cp.subject}".constantize   end end 

i have following concerns:

module ruby     extend activesupport::concern     def get_framework         'rails'     end end  module python     extend activesupport::concern     def get_framework         'django'     end end 

then, when run these separately, correct framework string:

python_book = book.create(:subject => 'python', :id => 1) python_book.get_framework -> 'django'  ruby_book = book.create(:subject => 'ruby', :id => 2) ruby_book.get_framework -> 'rails' 

my problem when have both of books returned in query, concern included last in result set , not picking correct concern methods.

books.all.order(:id => 'asc').collect |book|     puts book.get_framework end  # result ['rails', 'rails'] 

i assuming because 'include' happening @ class level , not instance level. love how clean , make work.

use .extend add instance methods instances of book instead.

extends in action:

module greeter   def say_hello     "hello"   end end 

---

irb(main):008:0> = object.new => #<object:0x00000101e01c38> irb(main):009:0> a.extend(greeter) => #<object:0x00000101e01c38> irb(main):010:0> a.say_hello => "hello" irb(main):011:0> object.new.say_hello nomethoderror: undefined method `say_hello' #<object:0x00000101e196d0> 

---

class book < activerecord::base   after_initialize |cp|     self.extend subject.constantize   end end