Модель пользователя не будет обновляться

Я пытаюсь обновить существующего пользователя:

Controller-Snippet

  def account_settings
    @user = current_user
  end

  def set_account_info
    old_user = current_user

    # verify the current password by creating a new user record.
    @user = User.authenticate_by_username(old_user.username, params[:user][:password])

    # verify
    if @user.nil?
      @user = current_user
      @user.errors[:password] = "Das eingegebene Passwort ist falsch."
      render :action => "account_settings"
    else
      # update the user with any new username and email
      @user.update(params[:user])
      # Set the old email and username, which is validated only if it has changed.
      @user.previous_email = old_user.email
      @user.previous_username = old_user.username

      if @user.valid?
        # If there is a new_password value, then we need to update the password.
        @user.password = @user.new_password unless @user.new_password.nil? || @user.new_password.empty?
        @user.save
        flash[:notice] = 'Benutzerkonto-Einstellungen wurden übernommen.'
        redirect_to :root
      else
        flash[:error] = @user.username
        render :action => "account_settings"
      end
    end
  end

Я уже пробовал post-, put- и patch-метод.

Route-Snippet

Calendar::Application.routes.draw do
  root "welcome#index"

  get "user/account_settings" => "user#account_settings"

  patch "user/account_settings" => "user#set_account_info"
end

Модель пользователя

class User < ActiveRecord::Base
  attr_accessible :email, :username, :previous_email, :previous_username, :password, :password_confirmation, :new_password, :new_password_confirmation
  attr_accessor :password, :new_password, :previous_email, :previous_username
  before_save :encrypt_password

  validates_confirmation_of :password
  validates_confirmation_of :new_password, :if => Proc.new {|user| !user.new_password.nil? && !user.new_password.empty? }
  validates_presence_of :password, :on => :create
  validates_presence_of :email, :if => Proc.new {|user| user.previous_email.nil? || user.email != user.previous_email}
  validates_presence_of :username, :if => Proc.new {|user| user.previous_username.nil? || user.username != user.previous_username}
  validates_uniqueness_of :email, :if => Proc.new {|user| user.previous_email.nil? || user.email != user.previous_email}
  validates_uniqueness_of :username, :if => Proc.new {|user| user.previous_username.nil? || user.username != user.previous_username}

  def initialize(attributes = {})
    super # must allow the active record to initialize!
    attributes.each do |name, value|
      send("#{name}=", value)
    end
  end

  def self.authenticate_by_email(email, password)
    user = find_by_email(email)
    if user && user.password_hash == BCrypt::Engine.hash_secret(password, user.password_salt)
      user
    else
      nil
    end
  end

  def self.authenticate_by_username(username, password)
    user = find_by_username(username)
    if user && user.password_hash == BCrypt::Engine.hash_secret(password, user.password_salt)
      user
    else
      nil
    end
  end

  def encrypt_password
    if password.present?
      self.password_salt = BCrypt::Engine.generate_salt
      self.password_hash = BCrypt::Engine.hash_secret(password, password_salt)
    end
  end
end

Flash-уведомление flash[:error] = @user.username ставит новое имя пользователя, поэтому я не понимаю, почему пользователь не обновляется в базе данных.
Сначала я подумал, что мой set_account_info-метод неверен, но я не знаю, как лучше проверить inputs.
Во-вторых, я изменил метод form_for с default(post) на put, а затем на patch, но это тоже не помогло.