Rails中使用好named_scope与时间区间

在我最近的工作中，由于要做数据统计，与时间区间打交道非常多，如统计这个月的销售量之类的。

Message.find(:all, :conditions => {:created_at => Time.now.beginning_of_month..Time.end_of_month})

对于爱美的程序员来说，这看起来不养眼，也不符合DRY精神。写成这种形式感觉 怎么样呢：

Message.in(:this_month) # 在一个named_scope中

来看看是如何做到这么DSLful的吧！

在config/initializer目录中创建timeranges.rb文件，如下：

# timeranges.rb
TimeRanges = {
  :today      => lambda { Time.now.beginning_of_day..Time.now.end_of_day },
  :yesterday  => lambda { 1.day.ago.beginning_of_day..1.day.ago.end_of_day },
  :this_week  => lambda { Time.now.beginning_of_week..Time.now.end_of_week },
  :last_week  => lambda { 1.week.ago.beginning_of_week..1.week.ago.end_of_week},
  :this_month => lambda { Time.now.beginning_of_month..Time.now.end_of_month },
  :last_month => lambda { 1.month.ago.beginning_of_month..1.month.ago.end_of_month }
}

在Model中创建一个名为in的named_scope：

class Message < ActiveRecord::Base
  named_scope :in, lambda { |period| 
      :conditions => {:created_at => TimeRanges[period].call}
  }
end

一个字，爽！

参考：http://workswithruby.com/2009/2/application-wide-timeranges-3

评论

4 楼 jayliud 2009-10-30  

看到kungfurails有类似的代码

class Message < ActiveRecord::Base
  named_scope :in, lambda { |period| 
      :conditions => {:created_at => 
         case period
         when 'today': Time.now.beginning_of_day..Time.now.end_of_day
         when 'yesterday ': 1.day.ago.beginning_of_day..1.day.ago.end_of_day
         end
   }
  }
end

3 楼 jayliud 2009-10-30  

class Message < ActiveRecord::Base
  named_scope :in, lambda { |period| 
      :conditions => {:created_at => 


   }
  }
end

2 楼 elele 2009-08-04  

1 楼 ssyangy 2009-07-20