Provide an extension for String's % method to call time#strftime if given argument is a Time object

string_format_with_strftime_extension.rb

# string_format_with_strftime_extension.rb
#
# Provide extension for String's % method to call Time%strftime when given argument
# is a Time object. So we can do <tt>"%d/%m/%Y" % Time.now</tt> and get the same
# result as <tt>Time.now.strftime "%d/%m/%Y"</tt>
#
# Put this file in #{RAILS_ROOT}/config/initializers so it will be automatically loaded.

class String
  alias_method :format_without_strftime_extension, :%
  
  # Format -- Apply formatting using <tt>str</tt> as a format specification and 
  # returns the result of applying it to <tt>arg</tt>. If the format specification 
  # contains more than one substitution, then <tt>arg</tt> must be an Array containing
  # the values to be substituted.
  #    
  #   "%05d" % 123                       #=> "00123"
  #   "%-5s: %08x" % [ "ID", self.id ]   #=> "ID   : 200e14d6"
  #
  # However, if the <tt>arg</tt> is an instance of Time, then Time#strftime will be 
  # called on <tt>arg</tt> by using <tt>str</tt> as an argument instead. This action
  # can be override by putting that Time instance into Array.
  #
  #   "%d/%m/%y" % Time.now.utc                   #=> "03/07/09"
  #   "Current timestamp is: %s" % Time.now.utc   #=> "Current timestamp is: 1246577322"
  #   "Today: %s" % [Time.now.utc]                #=> "Today: Fri Jul 03 06:29:19 UTC 2009"
  def %(arg)
    if arg.is_a? Array or !arg.is_a? Time
      format_without_strftime_extension(arg)
    else
      arg.strftime(self)
    end
  end
end