# "require" behaves differently in Rails vs vanilla Ruby? **URL:** \ **Category:** Rails\ **Created:** [March 18, 2010, 12:26am UTC](https://www.ruby-forum.com/t/require-behaves-differently-in-rails-vs-vanilla-ruby/185313 "2010-03-18T00:26:43Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Poco\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/4da419/32.png) [@Poco\_R](https://www.ruby-forum.com/u/Poco_R)\ **Post date:** [March 18, 2010, 12:26am UTC](https://www.ruby-forum.com/t/require-behaves-differently-in-rails-vs-vanilla-ruby/185313/1 "2010-03-18T00:26:43Z")
I can “require” a file from the console but not from irb or a simple ruby script. It’s not a path issue, the same file is found in both cases. So why is the module namespace an unrecognized constant sometimes and a valid module name others? Same .rb file both times. This one works: [chrisa@ibs-chrisa-ux1 lims\_m6.6]$ script/console Loading development environment (Rails 2.3.5) > > require ‘aibs/hotfix/logger’ > > [2010-03-17 13:50:02] INFO AIBS::Hotfix::Logger initialized at > > module load time > > =\> [] > > > exit … but this one bombs with a NameError. [chrisa@ibs-chrisa-ux1 lims\_m6.6]$ irb irb(main):001:0\> require ‘aibs/hotfix/logger’ NameError: uninitialized constant AIBS from /home/chrisa/depot/tech/lims\_m6.6/lib/aibs/hotfix/ logger.rb:1 from /local1/home/chrisa/rs\_base\_dev/ruby/lib/ruby/site\_ruby/ 1.8/rubygems/custom\_require.rb:31:in `gem_original_require' from /local1/home/chrisa/rs_base_dev/ruby/lib/ruby/site_ruby/ 1.8/rubygems/custom_require.rb:31:in`require’ from (irb):1 irb(main):002:0\> exit ---
**Author:** ![Poco\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/4da419/32.png) [@Poco\_R](https://www.ruby-forum.com/u/Poco_R)\ **Post date:** [March 18, 2010, 12:29am UTC](https://www.ruby-forum.com/t/require-behaves-differently-in-rails-vs-vanilla-ruby/185313/2 "2010-03-18T00:29:04Z")
On Mar 17, 8:56 pm, Poco R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I can “require” a file from the console but not from irb or a simple > ruby script. It’s not a path issue, the same file is found in both > cases. So why is the module namespace an unrecognized constant > sometimes and a valid module name others? When you run script/console a lot more is loaded that if you just run irb (eg plugins are loaded, rails is loaded, application initializers are loaded). In addition const\_missing is hooked which will automatically require stuff when a missing constant is found. Either of these could explain the difference between the two cases Fred ---
**Author:** ![Poco\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/4da419/32.png) [@Poco\_R](https://www.ruby-forum.com/u/Poco_R)\ **Post date:** [March 18, 2010, 12:53am UTC](https://www.ruby-forum.com/t/require-behaves-differently-in-rails-vs-vanilla-ruby/185313/3 "2010-03-18T00:53:39Z")
Thanks for helping me understand this. I get that lots of stuff gets loaded via the console, it certainly takes longer 😉 Here’s what’s really puzzling. It seems like the syntax is changing. Could this be an effect of the const\_missing hook? For example, I don’t even have to load a file. The console can handle the scoping on one line: [chrisa@ibs-chrisa-ux1 lims\_m6.6]$ script/console Loading development environment (Rails 2.3.5) > > module AIBS::Hotfix::Logger > > end > > =\> nil but irb can’t: [chrisa@ibs-chrisa-ux1 lims\_m6.6]$ irb irb(main):001:0\> module AIBS::Hotfix::Logger irb(main):002:1\> end NameError: uninitialized constant AIBS from (irb):1 irb(main):003:0\> [chrisa@ibs-chrisa-ux1 lims\_m6.6]$ what’s even weirder, instead of the ::**:: form, I nest them on different lines and voila:** [chrisa@ibs-chrisa-ux1 lims\_m6.6]$ irb irb(main):001:0\> module AIBS irb(main):002:1\> module Hotfix irb(main):003:2\> module Logger irb(main):004:3\> end irb(main):005:2\> end irb(main):006:1\> end =\> nil Yikes! This is all driven by a desire to use a bunch of (our) library code outside of the Rails framework i.e. for backend processing… Any pointers you could suggest that would help me get a grip on what’s going on would be greatly appreciated. On Mar 17, 4:27 pm, Frederick C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![Poco\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/4da419/32.png) [@Poco\_R](https://www.ruby-forum.com/u/Poco_R)\ **Post date:** [March 18, 2010, 10:29pm UTC](https://www.ruby-forum.com/t/require-behaves-differently-in-rails-vs-vanilla-ruby/185313/4 "2010-03-18T22:29:44Z")
Ah. Thanks, this makes (more) sense now. On Mar 18, 2:05 am, Frederick C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![Poco\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/4da419/32.png) [@Poco\_R](https://www.ruby-forum.com/u/Poco_R)\ **Post date:** [March 18, 2010, 10:06am UTC](https://www.ruby-forum.com/t/require-behaves-differently-in-rails-vs-vanilla-ruby/185313/5 "2010-03-18T10:06:09Z")
On Mar 17, 11:52 pm, Poco R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > different lines and voila: That’s not unexpected - the second form reopens (or creates) the AIBS module, whereas writing AIBS::Hotfix::Logger requires the AIBS and AIBS::Hotfix already exist. If they don’t exist then const\_missing is hit. Rails hooks this to try and load AIBS from somewhere (as long as there is a file named aibs.rb in one of the search paths this should work), apparently succeeding, whereas the default implementation just throws NameError > This is all driven by a desire to use a bunch of (our) library code > outside of the Rails framework i.e. for backend processing… The easy way here is to require config/environment which loads up rails for you. If you just want the const autoloading you can set that up to but you’ll have to delve into the Rails startup stuff to see how it initializes stuff. Fred