Build associations for User favorites' other users

I want to build a simple favorite system. I've found tutorial for polymorphic associations on the web but i'm sure there is a lot more simple !!

So I have a User model and I want to let users have has many other users as favorites. In the other way, a user may know who favored him.

I tried something like this:

class User < ActiveRecord::Base
  has_many :favorites, :class_name => 'User', :foreign_key => 'user_id'
  belongs_to :favorited_by, :class_name => 'User'
end

But I have an SQL error while doing

some_user.favorites << another_user

or

some_user.favorites.build(another_user)
some_user.save
some_开发者_JS百科user.favorites

Any help doing this simple thing... :)

Here is the trace:

ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: users.user_id: SELECT "users".* FROM "users" WHERE ("users".user_id = 1)
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/connection_adapters/abstract_adapter.rb:207:in `rescue in log'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/connection_adapters/abstract_adapter.rb:199:in `log'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/connection_adapters/sqlite_adapter.rb:135:in `execute'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/connection_adapters/sqlite_adapter.rb:284:in `select'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/connection_adapters/abstract/database_statements.rb:7:in `select_all'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/connection_adapters/abstract/query_cache.rb:56:in `select_all'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/base.rb:473:in `find_by_sql'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/relation.rb:64:in `to_a'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/relation/finder_methods.rb:143:in `all'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/associations/association_collection.rb:70:in `block in find'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/base.rb:1127:in `with_scope'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/associations/association_proxy.rb:207:in `with_scope'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/associations/association_collection.rb:63:in `find'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/associations/association_collection.rb:468:in `find_target'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/associations/association_collection.rb:398:in `load_target'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/activerecord-3.0.9/lib/active_record/associations/association_proxy.rb:145:in `inspect'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/commands/console.rb:44:in `start'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/commands/console.rb:8:in `start'
from /Users/pierrelouisgottfrois/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/commands.rb:23:in `<top (required)>'
from script/rails:6:in `require'

Answering my own thx to @Dogbert

Your model associations are wrong. Have a look at my answer here and adapt it for your use case.