Rails, update method and validation - ruby-on-rails

Question

I have a problem and I need an idea how to fix my update method. I have an admin panel where I can create users. This form include name, mail, password, repeated password fields and it works fine. Then I want to have a list of all users and to edit these who I want. The problem is that I want to edit part of the information which is not included in the form of the registration and default is empty. In edit mode my form has two new fields - notes and absences. When I change these fields and call update method I see message that password and repeated password don't match which is validation in the registration but I do not have these files in edit mode. How could I fix this problem. This is part of my code:
class UsersController < ApplicationController
def edit
#user = User.find(params[:id])
#title = "Edit user"
end
def update
#user = User.find(params[:id])
if #user.update_attributes(params[:user])
flash[:success] = "Profile updated."
redirect_to #user
else
#title = "Edit user"
render 'edit'
end
end
class User < ActiveRecord::Base
attr_accessor :password
attr_accessible :name, :email, :password, :password_confirmation
validates :name, :presence => true,
:length => { :maximum => 50 }
validates :email, :presence => true
email_regex = /\A[\w+\-.]+#[a-z\d\-.]+\.[a-z]+\z/i
validates :email, :presence => true,
:format => { :with => email_regex },
:uniqueness => true
validates :password, :presence => true,
:confirmation => true,
:length => { :within => 6..40 }
before_save :encrypt_password
def has_password?(submitted_password)
encrypted_password == encrypt(submitted_password)
end
def self.authenticate(email, submitted_password)
user = find_by_email(email)
return nil if user.nil?
return user if user.has_password?(submitted_password)
end
def self.authenticate_with_salt(id, cookie_salt)
user = find_by_id(id)
(user && user.salt == cookie_salt) ? user : nil
end
private
def encrypt_password
self.salt = make_salt unless has_password?(password)
self.encrypted_password = encrypt(password)
end
def encrypt(string)
secure_hash("#{salt}--#{string}")
end
def make_salt
secure_hash("#{Time.now.utc}--#{password}")
end
def secure_hash(string)
Digest::SHA2.hexdigest(string)
end
end

Answer 1

The validation for password presence is true when you are creating a user, but once a user has an encrypted password, you don't want to force it to be present in all form submissions in the future.
Active record supports adding conditions to validations, so I would suggest putting a condition on the password validation to make it only execute if the user object does not already have an encrypted password. The relevant snippet would be:
validates :password, :presence => true,
:confirmation => true,
:length => { :within => 6..40 },
:if => :needs_password?
def needs_password?
encrypted_password.nil?
end