Rails上一个星期日与任何DateTime关系 [英] Rails Previous Sunday in Relation to Any DateTime

问题描述

使用Rails 3应用程序。给定一个DateTime，我需要生成前一个星期天的日期时间。如果DateTime是星期天，那我想要那个星期天呢。以下是一些例子：

Working with a Rails 3 application. Given a DateTime, I need to produce the Datetime for the previous Sunday. If the DateTime is a Sunday, then I want that Sunday itself back. Here's some examples:

November 7, 2011 => November 6, 2011
November 6, 2011 => November 6, 2011
November 5, 2011 => October 30, 2011

任何想法？我有点卡住了

Any ideas? I'm a bit stuck.

推荐答案

class DateTime
  def previous_sunday
    self - wday
  end
end

...但是这样容易，没有理由将猴子修补到课程中：）

…but this is so easy, there's no reason to monkey patch it into the class :)

irb(main):001:0> require 'date'; now = DateTime.now
#=> #<DateTime: 2011-11-10T21:10:04-07:00 (…)>
irb(main):002:0> sunday = now - now.wday
#=> #<DateTime: 2011-11-06T21:10:04-07:00 (…)>

wday （工作日）将 0 任何星期日，所以不会更改日期。

The wday (weekday) will be 0 for any Sunday, and so no change to the date will take place.

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