validates_uniqueness_of before ActiveRecord::RecordNotUnique

Question

我在Rails 3.1.1应用程序中有以下类:

class User < ActiveRecord::Base  
  attr_accessible :email, :password, :password_confirmation, :remember_me, :username, :admin, :moderator, :bio
  validates_presence_of :username
  validates_uniqueness_of :username, :case_sensitive => false
  validates_uniqueness_of :email,  :case_sensitive => false

和我的迁移:

add_index :users, :email,                :unique => true
add_index :users, :username,             :unique => true

然而，当我尝试创建两个具有重复电子邮件或用户名的用户时，我得到一个DB级异常，而不是失败的验证:

ActiveRecord::RecordNotUnique in RegistrationsController#create
PGError: ERROR:  duplicate key value violates unique constraint "index_users_on_username"

有其他的验证工作完美，但为什么不唯一性验证在数据库创建之前执行?

Answer 1

试试这样:

class User < ActiveRecord::Base
  attr_accessible :email, 
              :password, 
              :password_confirmation, 
              :remember_me, 
              :username, 
              :admin, 
              :moderator, 
              :bio
  validates :username, :uniqueness => { :case_sensitive => false }, :presence => true
  validates :email,    :uniqueness => { :case_sensitive => false }