Polymorphic associations has_many :through

I’m facing an issue in polymorphic associations when i try to to
:through relationship.
I’ve three models:profile,gbluser,community


belongs_to :node ,:polymorphic => true
belongs_to :community,:class_name => “community”,
:foreign_key => “node_id”,
:conditions => “node_type = ‘community’”
belongs_to :gblorganization,:class_name => “gblorganization”,
:foreign_key => “node_id”,
:conditions => “node_type = ‘gblorganization’”
has_and_belongs_to_many :gblusers


has_many :communities,:through=>:profiles,:conditions =>
“profiles.node_type = ‘Community’”,:source=>:community


has_many :gblusers ,:class_name
=>“gbluser”,:through=>:profiles,:conditions => “profiles.node_type =

I’m trying to implement has_many :through relationship between community
and users.
user has_many communities through profiles and
communities has_many users through profiles

When i’m trying to do @user.communities, the search is made not on the
mapping table between user and profiles but on the profile table itself.
Rails is searching for user_id in profiles table but i’ve
has_and_belongs_to_many between profile and user.
How to solve this problem? Am I wrong somewhere. Please guide me.