ruby-on-rails - 我如何在 Ruby/Rails 中获得每月的第一个星期四？

Question

以下 Ruby 代码获取每个月的第一天:

require 'active_support/all'

# get the date at the beginning of this month
date = Date.today.beginning_of_month

# get the first day of the next 5 months
5.times do |num|
  date = date.next_month
  p date
end

给出:

=> Fri, 01 Aug 2014
=> Mon, 01 Sep 2014
=> Wed, 01 Oct 2014
=> Sat, 01 Nov 2014
=> Mon, 01 Dec 2014

但是我如何获得每个月的第一个星期四呢？即

=> Thu, 07 Aug 2014
=> Thu, 04 Sep 2014
=> Thu, 02 Oct 2014
=> Thu, 06 Nov 2014
=> Thu, 04 Dec 2014

Answer 1

不需要迭代或条件，只需得到所谓的直到下星期四的天数增量:

#4 is thursday because wday starts at 0 (sunday)

date = Date.today.beginning_of_month
date += (4 - date.wday) % 7
p date
=> Thu, 03 Jul 2014