ruby-on-rails – Ruby：给出一个日期,找到下一个第二或第四个星期二

我似乎无法找到一种优雅的方式来做到这一点……

在给定日期的情况下,如何找到下一个星期二,即该日历月的第二个或第四个星期二？

例如：

鉴于2012-10-19然后返回2012-10-23

要么

鉴于2012-10-31然后返回2012-11-13

October               November        
Su Mo Tu We Th Fr Sa    Su Mo Tu We Th Fr Sa  
    1  2  3  4  5  6                 1  2  3  
 7  8  9 10 11 12 13     4  5  6  7  8  9 10 
14 15 16 17 18 19 20    11 12 13 14 15 16 17  
21 22 23 24 25 26 27    18 19 20 21 22 23 24 
28 29 30 31             25 26 27 28 29 30

解决方法

如果您只想查看最终结果的样子,请滚动到底部.

使用我最近在ruby 1.9.3中完成的一些日期处理工作的代码片段.

对DateTime的一些升级：

require 'date'

class DateTime

  ALL_DAYS = [ 'sunday','monday','tuesday','wednesday','thursday','friday','saturday' ]

  def next_week
    self + (7 - self.wday)
  end

  def next_wday (n)
    n > self.wday ? self + (n - self.wday) : self.next_week.next_day(n)
  end

  def nth_wday (n,i)
    current = self.next_wday(n)
    while (i > 0)
      current = current.next_wday(n)
      i = i - 1
    end
    current
  end

  def first_of_month
    self - self.mday + 1
  end

  def last_of_month
    self.first_of_month.next_month - 1
  end

end

method_missing技巧：

我还补充了这个类,有一些方法缺少技巧来映射next_tuesday到next_wday(2)和first_tuesday(2)tonth_wday(2,2)`的调用,这使得下一个片段在眼睛上更容易.

class DateTime

  # ...

  def method_missing (sym,*args,&block)
    day = sym.to_s.gsub(/^(next|nth)_(?<day>[a-zA-Z]+)$/i,'\k<day>')
    dindex = ALL_DAYS.include?(day) ? ALL_DAYS.index(day.downcase) : nil
    if (sym =~ /^next_[a-zA-Z]+$/i) && dindex
      self.send(:next_wday,dindex)
    elsif (sym =~ /^nth_[a-zA-Z]+$/i) && dindex
      self.send(:nth_wday,dindex,args[0])
    else
      super(sym,&block)
    end
  end

  def respond_to? (sym)
    day = sym.to_s.gsub(/^(next|nth)_(?<day>[a-zA-Z]+)$/i,'\k<day>')
    (((sym =~ /^next_[a-zA-Z]+$/i) || (sym =~ /^nth_[a-zA-Z]+$/i)) && ALL_DAYS.include?(day)) || super(sym)
  end

end

例：

给定日期：

today = DateTime.Now
second_tuesday = (today.first_of_month - 1).nth_tuesday(2)
fourth_tuesday = (today.first_of_month - 1).nth_tuesday(4)

if today == second_tuesday
  puts "Today is the second tuesday of this month!"
elsif today == fourth_tuesday
  puts "Today is the fourth tuesday of this month!"
else
  puts "Today is not interesting."
end

您还可以编辑method_missing来处理调用,例如：second_tuesday_of_this_month,：fourth_tuesday_of_this_month等.如果我决定在以后编写代码,我会在此处发布代码.