current community

your communities

more stack exchange communities

Stack Exchange
tour help
stack overflow careers
Take the 2-minute tour ×
Stack Overflow is a question and answer site for professional and enthusiast programmers. It's 100% free, no registration required.
up vote 0 down vote favorite

I think I understand the basics of requiring and including modules* in Ruby on Rails, but I can't figure out what's going on with an issue I'm having. I'm using Ruby 1.9.3 with Rails 3.2.1.

I have a module called Utils in /lib/_utils.rb, which currently just has some logging functions in it. In most other files in the app, I'm able to execute the following code and use the logger without any problem:

logger = Utils::SingletonLogger.get_logger

Note that in model code, I generally use an instance variable instead of a local variable, and that seems to work fine as well.

Also note that this does NOT require me to have

include Utils

in the code.

The problem is that, in at least one controller, I have to explicitly require and include the module before it will work. Well, usually anyway. Most of the time I get a NameError because it doesn't recognize Utils as a constant. Other times, it throws a ransack error. And once it a great while, it just works. If I add just the include Utils line, I get a similar NameError, though with a shorter error message.

And best of all, this only happens in the test environment, and not in my local dev instance.

For now, I've commented out all the logging in this one file, but I'd like to understand what's going on. I've added 

config.autoload_once_paths += %W(#{config.root}/lib)

to application.rb, thinking this would insure that the actual code is available to any file in the application. I guess I'm supposed to need

include Utils

in every file that uses this module, but I don't understand why that doesn't seem to be required in other files, or why I should have to re-require the module file in this controller.

I'd appreciate any insight or guidance.

*Briefly - require/load reads the module's actual source code file into memory, include makes the module's methods available in a different file. I assume that I really only want to require/load a file once per instance of the application - that having it executed every time a new class is used is unsightly at best, and inefficient at worst.

share|improve this question
    
What's the error? Add the following line to application.rb file and restart your server config.autoload_paths += %W(#{config.root}/lib) –  Nicolas Garnil Feb 5 at 15:03
    
Is it better to use config.autoload_paths than config.autoload_once_paths? The error is usually a NameError, that the constant Utils is not defined. I can get the exact message if you like, but the issue is that "Utils" is not recognized. –  whognu Feb 5 at 16:08
    
keep using autoload_once_paths. did you restart the server? –  Nicolas Garnil Feb 5 at 16:15
    
Yes, I restart it every time I deploy changes. –  whognu Feb 5 at 16:33

1 Answer 1

up vote 0 down vote

I think the problem involved some combination of the following:

  • The module's file name didn't match the name of the module, so it didn't get picked up by the autoload.
  • I had an explicit require statement in a couple of files, but not others. I think when the files containing the require were executed before ones that weren't, the system could find the module, otherwise, it couldn't.
  • At least during the troubleshooting, I sometimes had the include statement outside of class definitions, which apparently is non-standard at best, meaningless at worst.
  • I used the module name as a prefix, which seems to work okay when everything else is set up correctly, but may have confused the interpreter at other times. I think this is standard when calling module methods directly, and it may mean that you don't have to include the module, though I'm not sure on that point yet.
  • I had a model's initialize method overridden, which may not have contributed to this problem, but did throw exceptions that interfered with debugging.

I still don't know why this flaked out in test, but not in dev.

share|improve this answer
    
Also, note that require returns false not only if there's an error loading the file, but also if the file has already been successfully loaded, and just doesn't need to be loaded again. That was a red herring in my troubleshooting for a while. –  whognu Feb 7 at 15:32

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.