NoMethodError：未定义的方法`validate＆＃39; （自定义验证）RAILS 3

Question

my item.rb

# encoding: utf-8
class Item < ActiveRecord::Base
  attr_accessible :asin, :domain, :formatted_price, :user_id

  validate :double_dates

private

  def double_dates
    if Item.where(:user_id => self.user_id, :asin => self.asin, :domain => self.domain).where("DATE(created_at) = ?", Date.today).length == 1
      errors.add(:created_at, "no double dates")
    end
  end

end

错误讯息：

    from script/rails:6:in `<main>'irb(main):028:0> Item.new
NoMethodError: undefined method `  validate' for #<Class:0x007fb054ce7690>
    from .rvm/gems/ruby-1.9.3-p327/gems/activerecord-3.2.13/lib/active_record/dynamic_matchers.rb:55:in `method_missing'
...

Answer 1

既然回答了，就发一个真正的答案：

`validate'看起来很奇怪，必须删除v之前的特殊字符。