auto load

Posted by jcarroll

Aug 07

One thing I never looked too far into Rails was: what of my files in lib do I need to require in and what don’t I need to require in?

It turns out that if you follow some naming conventions you can avoid require‘ing files in, which can help keep your various environment files shorter.

If you have a class or module in lib who’s name follows the Ruby conventions of MixedCase and who’s file name is the lower case, words separated by underscores pattern, used by your Rails generated files, then it will be require‘d automatically.

For example, the following files will be require‘d automatically by Rails, there’s no need to require them in any environment file.

lib/query.rb 
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class Query
end
lib/string_extensions.rb 
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module StringExtensions
end

If you want to package your libraries in subdirectories in lib, those too can still be loaded automatically if you follow some conventions. Any directories must correspond to modules and you have to follow the same naming convention mentioned above.

For example, the following file will be require‘d automatically by Rails: lib/foo/bar.rb 
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module Foo

  class Bar
  end

end

Comments on this post

Shadowfiend

Aug 07

Shadowfiend said,

The question is, of course, whether these are automatically required at startup or when the constant is called up via const_missing. I think it’s the latter, but I’m not sure…

Joseph

Aug 08

Joseph said,

This sub-directory convention pertains to models, controllers and helpers as well. If you want to organise your models directory, you can put them in modules and then move them into sub-directories based on the module name.

I tend not to put models inheriting from ActiveRecord::Base into modules, but it’s useful for distinguishing and grouping non-ActiveRecord classes.

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