---
title: auto load
teaser: How to name libraries for autoloading in Rails.
tags: web,rails
author: Jared Carroll
published_on: 2007-08-08
---

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.

In `lib/query.rb`:

```ruby
class Query
end
```

In `lib/string_extensions.rb`:

```ruby
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:

In `lib/foo/bar.rb`:

```ruby
module Foo

  class Bar
  end

end
```