require

Here are some different ways to require stuff in ruby. The funny ones courtesy of why the lucky stiff.

require "rubygems"
require "open-uri"
require "yaml"

[ "rubygems", "open-uri", "yaml" ].each { |s| require s }

%w[rubygems open-uri yaml].map(&method(:require))

File.dirname(__FILE__)

What got me looking at require was how annoying it is to use the File.dirname(__FILE__) syntax all the time in init.rb’s, like:

require File.dirname(__FILE__) + "/parser/black_cat"
require File.dirname(__FILE__) + "/parser/dar"
require File.dirname(__FILE__) + "/parser/dc_nine"
require File.dirname(__FILE__) + "/parser/iota"
require File.dirname(__FILE__) + "/parser/jammin_java"

I am always just verbose with requires, I don’t know why. It gets even less readable if you start using File.join(...). I was poking around in the rails source to see how they do requires and they use $::

$:.unshift(File.dirname(__FILE__)) unless
  $:.include?(File.dirname(__FILE__)) || $:.include?(File.expand_path(File.dirname(__FILE__)))

require 'action_controller/base'
require 'action_controller/request'
require 'action_controller/rescue'
...

$:

What is $:?

irb(main):001:0> $:
=> ["/usr/local/lib/ruby/site_ruby/1.8", "/usr/local/lib/ruby/site_ruby/universal-darwin8.0",
"/usr/local/lib/ruby/site_ruby/1.8/universal-darwin8.0", "/usr/local/lib/ruby/site_ruby",
"/usr/local/lib/ruby/1.8", "/usr/local/lib/ruby/1.8/universal-darwin8.0",
"/usr/local/lib/ruby/1.8/universal-darwin8.0", "."]

Its the load path. It turns out $LOAD_PATH is a synonym. So that would take me:

$LOAD_PATH.unshift(File.dirname(__FILE__))

require "parser/black_cat"
require "parser/dar"
require "parser/dc_nine"
require "parser/iota"
require "parser/jammin_java"

But is this a bad idea? What if the load path gets large? Do we care?