ruby on rails - Limit create action to 1 post per user -

i want make user have 1 matriculation per user. error "undefined method `matriculations' nil:nilclass". how make work? (i use devise user auth if matter).

 def matriculation_limit   if self.user.matriculations(:reload).count <= 1     errors.add(:base, "yuo have 1 matriculation form")   else     redirect_to new_matriculation_path   end  end 

with has_one association, association finder method singular @user.matriculation, not @user.matriculations. , there's no point counting them because there one.

regarding comment:

you don't need check anywhere how many matriculations user has, because it's singular association, you'll updating association (changing id in foreign key column matriculation_id in users table)

class user < activerecord::base   has_one :matriculation, :class_name => "user", :foreign_key => "matriculation_id" end  class matriculation < activerecord::base   belongs_to :user end  # controller action...   @user.matriculation = matriculation.find(params[:matriculation_id]) # or something!