Clarification of what Ruby's 'require' does - ruby

Question

A heads up that I'm in no way a Ruby expert...I just use it from time to time for basic scripting. I'm trying to use the RubyCocoa framework so that I can use additional commands in my Ruby script.
As an example, if I was to try something as explicit as this:
#!/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby
require '/System/Library/Frameworks/RubyCocoa.framework/Versions/A/Resources/ruby/osx/cocoa.rb'
puts "Hello, World"
I receive this error:
/usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- osx/objc/cocoa.rb (LoadError)
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from /System/Library/Frameworks/RubyCocoa.framework/Versions/A/Resources/ruby/osx/cocoa.rb:8:in `<top (required)>'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from /usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from Test.rb:4:in `<main>'
I do have Homebrew installed on my Mac (running 10.10), but why does the require command go through to the Cellar folder? You can see I'm trying to use the 2.0 Ruby version from my Frameworks folder (the one in /usr/bin is still 1.9.3 (would also love for someone to explain how these versions differ and why)).

Answer 1

It goes through the Cellar folder because it is in your load path.
You can examine your load path by writing in your script
puts $:
Concerning your error message
You can use fully qualified path in require so
require '/System/Library/Frameworks/RubyCocoa.framework/Versions/A/Resources/ruby/osx/cocoa.rb'
is correct.
And indeed in your error message you can see this line
from /System/Library/Frameworks/RubyCocoa.framework/Versions/A/Resources/ruby/osx/cocoa.rb:8:in `<top (required)>'
So you correctly required your file
However from the first line of your error message.
usr/local/Cellar/ruby/1.9.3-p194/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- osx/objc/cocoa.rb (LoadError)
We can see ruby/osx/cocoa.rb tries to require another file. This one is different and found under osx/objc/cocoa.rb. So those files have similar names but are different.
And since it tries to require with require 'osx/objc/cocoa.rb' it fails because it does not know how to find it (not a fully qualified path here).
Maybe you can try to change the load path variable.
By adding the line:
$: << '/System/Library/Frameworks/RubyCocoa.framework/Versions/A/Resources/ruby/osx/objc/'
It might work but I’m not sure since I don’t know where that osx/obj folder is located on your machine.
you might want to take some time to clean your ruby installation and maybe instead a fresh ruby using rvm or rbenv (I prefer rbenv)