在工作曾遇到一個問題

time1 = Time.current
time2 = Time.zone.today.advance(days: -7).end_of_week

time1 > time2 
# => true 

time2 > time1
# => ArgumentError: comparison of Date with ActiveSupport::TimeWithZone failed

(Rails 6 有解決了)
因為我們公司是用Rails 3，我想說兩個時間物件，怎麼會一下子可以比大小，不過換個順序就不行了？

原來：

Time.current.class
# => ActiveSupport::TimeWithZone 

Time.zone.today.advance(days: -7).end_of_week.class
# => Date 

一個是 Rails 類別 ActiveSupport::TimeWithZone
一個是 Ruby 類別 Date

在Rails 3，Date類別的:>方法可比較類別沒有 ActiveSupport::TimeWithZone。但是 TimeWithZone 的可比較類別有Date，也就是遇到Date類別，TimeWithZone會幫他自動轉換。

怎麼解決這個問題？

使用:to_datetime方法，都轉成 DateTime 物件

time1 = Time.current
# => Tue, 22 Sep 2020 15:49:55 UTC +00:00 
 
time1.to_datetime
# => Tue, 22 Sep 2020 15:49:55 +0000 

time1.to_datetime.class
 => DateTime 

time2 = Time.zone.today.advance(days: -7).end_of_week
# => Sun, 20 Sep 2020 

time2.to_datetime
# => Sun, 20 Sep 2020 00:00:00 +0000

time2.to_datetime.class
# => DateTime 
 
time2 > time1
# => false  

總算可以將兩個時間作比較了