From: Leslie Viljoen <leslieviljoen@...>
Date: 2008-05-30T00:21:42+09:00
Subject: Surprising Extend

Hi people

I want to make a library which can extend the String class. I don't want to
keep putting the class String; def blah; end; end; at the top of all my
files, I just want to require 'StringExt'

This doesn't work, after I have 'require'd it into my file:

class String
	def to_hex
		unpack("C*").map{|b| b.to_s(16)}.join(" ")
	end
end

So I tried this:

module StringExt
	def to_hex
		unpack("C*").map{|b| b.to_s(16)}.join(" ")
	end
end
----
then in my file I put: require 'StringExt'; String.extend StringExt
..but that didn't work.

Then I tried:
s = "sdfdsfsdfsdF"
s.extend StringExt
s.to_hex

...but that didn't work.

In the Pragmatic Programmer there's an example, but the module is
defined in the same file as where it's used - and only the s.extend...
version then works.

I really want String.extend, to change all strings. How do a 'require'
a file that then changes the String class?

Les