Rails：錯誤「NoMethodError：未定義的方法`<'for nil：NilClass」，缺少一些寶石？

這裏是模型類類項目::項目<的ActiveRecord :: Base的 validates_presence_of：起始日期，時間：END_DATE，：PRODUCT_ID 驗證：validate_start_and_end_dateRails：錯誤「NoMethodError：未定義的方法`<'for nil：NilClass」，缺少一些寶石？

  def validate_start_and_end_date 
      errors.add(:start_date, "should not be in past") if start_date < Date.today 
      errors.add(:end_date, "should not be in past") if end_date < Date.today 
      errors.add(:base, "start date should not be after end date") if end_date < start_date 
     end 

     belongs_to :product, {:class_name => 'Item::Product'} 

    end

這裏是日誌軌控制檯

ruby-1.8.7-p334 :020 > item = Item::Item.new 
    => #<Item::Item id: nil, start_date: nil, end_date: nil, product_id: nil> 
    ruby-1.8.7-p334 :021 > item.valid? 
    NoMethodError: undefined method `<' for nil:NilClass 
    from /home/maddy/.rvm/gems/ruby-1.8.7-p334/gems/activesupport-3.0.3/lib/active_support/whiny_nil.rb:48:in `method_missing' 
    from /media/Development/codie/orgstud-security/app/models/lecture/lecture.rb:13:in `validate_start_and_end_date' 
    from /home/maddy/.rvm/gems/ruby-1.8.7-p334/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:419:in `_run_validate_callbacks' 
    from /home/maddy/.rvm/gems/ruby-1.8.7-p334/gems/activemodel-3.0.3/lib/active_model/validations.rb:212:in `run_validations!' 
    from /home/maddy/.rvm/gems/ruby-1.8.7-p334/gems/activemodel-3.0.3/lib/active_model/validations/callbacks.rb:67:in `run_validations!' 
    from /home/sgarg/.rvm/gems/ruby-1.8.7-p334/gems/activesupport-3.0.3/lib/active_support/callbacks.rb:413:in `_run_validation_callbacks' 
    from /home/maddy/.rvm/gems/ruby-1.8.7-p334/gems/activemodel-3.0.3/lib/active_model/validations/callbacks.rb:67:in `run_validations!' 
    from /home/maddy/.rvm/gems/ruby-1.8.7-p334/gems/activemodel-3.0.3/lib/active_model/validations.rb:179:in `valid?' 
    from /home/maddy/.rvm/gems/ruby-1.8.7-p334/gems/activerecord-3.0.3/lib/active_record/validations.rb:55:in `valid?' 
from (irb):21

來源

2011-03-21 Maddy.Shik

請注意，您在控制檯中創建的對象具有start_date,end_date等nil。

然後，您的驗證方法中nil < Date.today的比較引起異常。

來源

2011-03-21 22:54:58

我剛纔看到的第一個代碼塊來說明'講座:: Lecture'模型。你可以發佈'Item :: Item'模型嗎？（這可能是同樣的問題，但我不能確定。） – 2011-03-21 22:58:58

這是抱怨，因爲start_date和end_date屬性在您的自定義驗證時尚未設置。當它試圖比較start_date和今天的日期時，它試圖比較一個零值。

你可以換你驗證的條件塊：

if !start_date.nil? && !end_date.nil? 
    ... 
end

來源

2011-03-21 22:56:29

'除非start_date.nil？ && end_date.nil？' – Noz 2013-04-22 20:19:48

Rails：錯誤「NoMethodError：未定義的方法`<'for nil：NilClass」，缺少一些寶石？

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