From: Sylvester Keil <sylvester.keil@...>
Date: 2011-11-05T21:54:57+09:00
Subject: Re: Are there two kinds of 'require' ?


On Nov 5, 2011, at 1:26 PM, Kaye Ng wrote:

> I'm reading a tutorial and it has an example like this"
> 
> require 'rubygems'
> require 'RedCloth'
> 
> The tutorial says:
> "...the RubyGems library over-rides the require method and enables it to
> be used to
> 
> load gems as if they were normal, local libraries."
> 
> I don't know how it works.
> 
> Is there a rubygems require and an ordinary require?

The salient point is that require depends on your LOAD_PATH. There are many ways to inspect your load path, for example, you can start irb and look at the $: global variable. If you use require with a name like 'string_extensions' it searches your load path for a matching file (it adds 'rb' or the appropriate extension file extension automatically). Basically, you can think of requiring 'rubygems' as adding all your installed gems to the load path so that they will be found if you require them.

Most developers (in my experience) discourage the use of explicitly requiring ruby gems in libraries. For a detailed explanation see: https://gist.github.com/54177

Whenever you require one of your files and it can't be found, it means that the file isn't in your current load path. For that reason, Ryan Davis above suggested you use ruby -I. (this explicitly adds your working directory to the load path) and Luke Gruber explained how you can use require with an absolute path.


> I'm using 1.9.2 and I know *require 'rubygems'* is not necessary as
> RubyGems is loaded
> 
> by default.  But I still don't understand the logic behind the
> "over-rides the require
> 
> method and enables it to be used to load gems as if they were normal,
> local libraries"
> 
> part.
> 
> 1.  Does RedCloth have the .rb suffix? Is it different from any simple
> library I can
> 
> make (e.g. string_extensions.rb) in that it has to use the rubygems
> version of
> 
> 'require'?
> 
> 2.  Regarding the 'string_extensions.rb' , is RubyGems even necessary?
> That is, does
> 
> the automatically-loaded RubyGems have any bearing on simple libraries
> that I may
> 
> create? Or is it just for downloaded gems like RedCloth?
> 
> Can someone please explain it to me in simple terms?
> 
> Thank you. =)
> 
> -- 
> Posted via http://www.ruby-forum.com/.
>