Creating an empty profile on devise registration - ruby-on-rails

Question

I have used devise for authentication in a rails app and I want a user to be able to sign up and once signed up be able to edit their own profile. I've followed along with other answers on stack but when I try and register using the default devise registration form I'm getting this error.
NoMethodError in Devise::RegistrationsController#create
undefined method `create' for nil:NilClass
app/models/user.rb:17:in `create_profile'
My User.rb is as follows
class User < ActiveRecord::Base
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
has_one :profile
attr_accessible :login, :username, :email, :password, :password_confirmation, :remember_me, :profile_attributes
attr_accessor :login
accepts_nested_attributes_for :profile
validates :username, :uniqueness => { :case_sensitive => false }, :presence => true
after_create :create_profile
def create_profile
self.profile.create
end
def self.find_first_by_auth_conditions(warden_conditions)
conditions = warden_conditions.dup
if login = conditions.delete(:login)
where(conditions).where(["username = :value OR lower(email) = lower(:value)", { :value => login }]).first
else
where(conditions).first
end
end
end
Profile.rb is
class Profile < ActiveRecord::Base
attr_accessible :fax, :phone_1, :phone_2, :url
belongs_to :user
end
profiles controller is the norm apart from the edit action
def edit
#profile = current_user.profile
end

Answer 1

You need to use self.create_profile instead of self.profile.create for has_one association.
Example
An Account class declares has_one :beneficiary, which will add:
Account#beneficiary (similar to Beneficiary.where(account_id: id).first)
Account#beneficiary=(beneficiary) (similar to beneficiary.account_id = account.id; beneficiary.save)
Account#build_beneficiary (similar to Beneficiary.new("account_id" => id))
Account#create_beneficiary (similar to b = Beneficiary.new("account_id" => id); b.save; b)
Account#create_beneficiary! (similar to b = Beneficiary.new("account_id" => id); b.save!; b)
More docs here