ruby on rails - Ransack's collection_select and HABTM return undefined method -

i've been looking on code on , on again , can't see problem.

i have 2 models person , credential. have habtm relationship.

person

class person < activerecord::base   attr_accessible :credential_ids    has_and_belongs_to_many :credentials    unransackable_attributes = ["id", "hidden_note", "created_at", "updated_at"]    def self.ransackable_attributes auth_object = nil     (column_names - unransackable_attributes) + _ransackers.keys   end end 

credential

class credential < activerecord::base   attr_accessible :description, :name   has_and_belongs_to_many :people    unransackable_attributes = ["id", "created_at", "updated_at"]    def self.ransackable_attributes auth_object = nil     (column_names - unransackable_attributes) + _ransackers.keys   end  end 

and here's form in people index.html.erb:

<%= search_form_for @search, :class => 'no-bottom-margin form-inline' |f| %>     %= f.collection_select(:credentials_id_eq , credential.all, :id, :name )%>     <div class='actions'><%= f.submit "search", :class => 'btn btn-primary btn-large' %></div> <% end %> 

and lastly, error i'm getting.

undefined method `credentials_id_eq' #<ransack::search:0x00000105aa4f28> 

so if make model's attribute unracksackable so:

unransackable_attributes = ["id", "created_at", "updated_at"] 

you can't use ransack's :model_attribute_predicate function particular attribute. so, :credentials_id_eq

it's pretty obvious now, wanted to hide id user when making custom query, make available myself. changed ransack function :credentials_name_cont , worked fine. also, removing id list of unracksackable attributes work.