At some point in tinkering with a language, you outgrow simple scripts and want to organize your code into separate modules that live in separate files. It's just this little OCD code habit you develop. Since I've only been using Ruby with Rails up till now, loading and importing the correct library files have been completely hidden away by Rails convention and magic. Everytime I want to use a library named 'acts_as_giraffe', I either A) assumed it was loaded already, or B) do require 'acts_as_giraffe'. But the real world's not so easy.
Like other languages, Ruby has a concept of a load-path where it'll search for .rb files to require. To see what this defaults to, run the following:
ruby -e 'puts $LOAD_PATH'
The shorter, perlish version is to use $: instead of $LOAD_PATH. This variable is just an array of directory names to search when require is called. To add or remove load paths, just mutate the list with shift and unshift. To see what Rails magic provides you, go to a Rails project, and run script/console and print $:
Amazing isn't it? For my housing project that uses Edge Rails, I see that the precendence for loading libraries is something along the lines of:
This is a much longer list of paths to look for a library compared to the first run I did on the command line.
What I like about this magic is that it keeps most of my code clear from hardcoded or semi-hardcoded absolute paths like the following:
require File.expand_path(File.dirname(__FILE__) + "/../config/environment")
The first hit on google about the topic is a pretty good explanation of the problem. I agree that a single giant 'require farm' is hard to unmaintain and pretty unsightly, but I do think that small require farms that are associated with specific modules and directories are a good way to organize. For example, if I had a library called 'obfuscator' that lives in many separate files:
obfuscator/ crypt.rb cram.rb barf.rb
I'd add an 'obfuscator.rb' file that globed all the rb files and required them:
Dir.glob(File.join('obfuscator', '*.rb')).each do |lib| require lib end
Then whenever I wanted to use obfuscator, I'd simply require 'obfuscator.rb'. The above would work if your current working directory is the same as obfuscator.rb. Unfortunately, if it isn't, then you're screwed because require won't be able to find obfuscator/*.rb relative to where you are.
One fix is to hard code the glob to be relative to the current file, rather than the current working directory:
Dir.glob(File.join(File.dirname(__FILE__), 'obfuscator', '*.rb')).each do |lib| require lib end
This will make the library lookups relative to 'obfuscator.rb' (FILE). Since it's semi-hardcoded it'll work.
Another solution that I came across today that I liked is to have the library to-be-loaded be in charge of doing the requiring. I noticed that Webby also used a similar trick called ensure_in_path to calculate some library loading:
# Adds the given arguments to the include path if they are not # already there def ensure_in_path( *args ) args.each do |path| path = File.expand_path(path) $:.unshift(path) if test(?d, path) and not $:.include?(path) end end
I'll keep an eye out for other clean ways people have been approaching this problem, but so far I like the approach of manipulating the load path in a function or file, and having that function or file loaded before the rest of the project. I hope that clears up some requiring woes!