app-models-user.rb - self.find_for_twitter_oauth

#app/models/user.rb
def self.find_for_twitter_oauth(auth, signed_in_resource=nil)
    user = User.where(:provider => auth.provider, :uid => auth.uid).first
    unless user
      user = User.create(user_nickname:     auth.info.nickname,
                         provider: auth.provider,
                         uid:      auth.uid,
                         email:    User.create_unique_email,
                         password: Devise.friendly_token[0,20]
                        )
    end
    user
  end