"require" behaves differently in Rails vs vanilla Ruby?

Rails
1

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:inrequire’
from (irb):1
irb(main):002:0> exit

2

On Mar 17, 8:56 pm, Poco R. [email protected] 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

3

Thanks for helping me understand this. I get that lots of stuff gets
loaded via the console, it certainly takes longer :wink:

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. [email protected]

4

Ah. Thanks, this makes (more) sense now.

On Mar 18, 2:05 am, Frederick C. [email protected]

5

On Mar 17, 11:52 pm, Poco R. [email protected] 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