From: Brian Candler <b.candler@...>
Date: 2009-01-13T21:13:42+09:00
Subject: Re: extending strftime

Lin Wj wrote:
> can i change the options which is recognized by strftime
> eg:
> '%Y %m %d'  will apply the format of YYYY mm dd
> 
> can i do something like extending strftime to recognize 'YYYY mm dd'
> instead ?
> 
> because right now , i am running the format string which i get(YYYY mm
> dd) through a regex and converting them to the parameters which strftime
> recognizes

That sounds like a perfectly reasonable approach.

If you really want to, you can monkey-patch the built-in class (I'd 
advise against this though, except in small self-contained scripts)

class Time
  alias :old_strftime :strftime
  STRFMAP = {
    'YYYY' => '%Y',
    'mm' => '%m',
    'dd' => '%d',
  }
  STRFRE = /#{STRFMAP.keys.join("|")}/

  def strftime(arg)
    old_strftime(arg.gsub(STRFRE) { STRFMAP[$&] })
  end
end

puts Time.now.strftime("YYYY-mm-dd")

Note that by not using the % escape syntax, you may end up with some 
subtle bugs:

puts Time.now.strftime("Today's YYYY-mm-dd, buddy!")
# => Today's 2009-01-13, bu13y!

You can restrict the regular expression to require a word boundary:

  STRFRE = /\b(#{STRFMAP.keys.join("|")})\b/

But in this case, a string like "YYYYmmdd" doesn't work.
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