Validation failed: Password can't be blank - ruby-on-rails

Question

I have an app, build on Rails 4.2 and tried to do twitter authentication, using RailsCasts #241 Simple OmniAuth.
But have this issue: Validation failed: Password can't be blank!
I searched answer everywhere, but did not find the solution!
user.rb
class User < ActiveRecord::Base
has_secure_password
validates :password, length: { minimum: 6 }, allow_blank: true
def self.create_with_omniauth(auth)
create! do |user|
user.provider = auth.provider
user.uid = auth.uid
user.name = auth.info.name
end
end
end
sessions_controller.rb
class SessionsController < ApplicationController
def login
end
def create
#user = User.find_by_email(params[:email])
if #user && #user.authenticate(params[:password])
session[:user_id] = #user.id
redirect_to root_path
else
redirect_to :back
end
end
def create_session
auth = request.env['omniauth.auth']
user = User.find_by_provider_and_uid(auth['provider'], auth['uid']) || User.create_with_omniauth(auth)
session[:user_id] = user.id
redirect_to root_url, notice: 'Signed in!'
end
def logout
reset_session
redirect_to root_path
end
end
routes.rb
get 'sessions/login'
get 'sessions/logout'
post 'sessions' => 'sessions#create'
get '/auth/:provider/callback' => 'sessions#create_session'
post '/auth/:provider/callback' => 'sessions#create_session'
get 'registration' => 'users#new', as: 'registration'
Solution
After editing user.rb model looks like:
class User < ActiveRecord::Base
has_secure_password
validates :password, length: { minimum: 6 }
require 'securerandom'
def self.create_with_omniauth(auth)
create! do |user|
user.provider = auth.provider
user.uid = auth.uid
user.name = auth.info.name
user.password = SecureRandom.urlsafe_base64
end
end
end

Answer 1

An alternative approach is to enter a random password on user creation. For example as shown in the omniauth-google-oauth2 readme. So you could alter your code to this:
require 'securerandom'
def self.create_with_omniauth(auth)
create! do |user|
user.provider = auth.provider
user.uid = auth.uid
user.name = auth.info.name
user.password = SecureRandom.urlsafe_base64
end
end

Answer 2

I think it's problem with
has_secure_password
try commenting it, and you can override the has_secure_password Or
has_secure_password(validations: false)
This is happening as it automatically adds
validates_presence_of :password_digest
So when specify allow_blank or allow_null it will not work