module Devise::Models::DatabaseAuthenticatable

def self.included(base) 

def self.included(base)
  base.class_eval do
    extend ClassMethods
    attr_reader :password, :current_password
    attr_accessor :password_confirmation
  end
end

def clean_up_passwords

Set password and password confirmation to nil 
def clean_up_passwords
  self.password = self.password_confirmation = nil
end

def old_password

TODO Remove me in next release 
def old_password
  ActiveSupport::Deprecation.warn "old_password is deprecated, please use current_password instead", caller
  @old_password
end

def password=(new_password)

and then trigger any "after_changed_password"-callbacks.
Regenerates password salt and encrypted password each time password is set, 
def password=(new_password)
  @password = new_password
  if @password.present?
    self.password_salt = self.class.encryptor_class.salt
    self.encrypted_password = password_digest(@password)
  end
end

def password_digest(password)

Digests the password using the configured encryptor. 
def password_digest(password)
  self.class.encryptor_class.digest(password, self.class.stretches, self.password_salt, self.class.pepper)
end

def password_required?

or confirmation are being set somewhere.
Passwords are always required if it's a new record, or if the password
Checks whether a password is needed or not. For validations only. 
def password_required?
  new_record? || !password.nil? || !password_confirmation.nil?
end

def update_with_password(params={})

:password_confirmation if they are blank.
error on :current_password. It also automatically rejects :password and
Update record attributes when :current_password matches, otherwise returns 
def update_with_password(params={})
  current_password = params.delete(:current_password)
  if params[:password].blank?
    params.delete(:password)
    params.delete(:password_confirmation) if params[:password_confirmation].blank?
  end
  result = if valid_password?(current_password)
    update_attributes(params)
  else
    message = current_password.blank? ? :blank : :invalid
    self.class.add_error_on(self, :current_password, message, false)
    self.attributes = params
    false
  end
  clean_up_passwords unless result
  result
end

def valid_for_authentication?(attributes)

Checks if a resource is valid upon authentication. 
def valid_for_authentication?(attributes)
  valid_password?(attributes[:password])
end

def valid_password?(incoming_password)

Verifies whether an incoming_password (ie from sign in) is the user password. 
def valid_password?(incoming_password)
  password_digest(incoming_password) == self.encrypted_password
end