Auto-loading lib files in Rails 4

I think this may solve your problem:

1. in config/application.rb:

   config.autoload_paths << Rails.root.join('lib')
   

   and keep the right naming convention in lib.

   in lib/foo.rb:

   class Foo
   end
   

   in lib/foo/bar.rb:

   class Foo::Bar
   end
   

2. if you really wanna do some monkey patches in file like lib/extensions.rb, you may manually require it:

   in config/initializers/require.rb:

   require "#{Rails.root}/lib/extensions" 
   

P.S.

• Rails 3 Autoload Modules/Classes by Bill Harding.

• And to understand what does Rails exactly do about auto-loading?
  read Rails autoloading — how it works, and when it doesn't by Simon Coffey.

This might help someone like me that finds this answer when searching for solutions to how Rails handles the class loading ... I found that I had to define a module whose name matched my filename appropriately, rather than just defining a class:

In file lib/development_mail_interceptor.rb (Yes, I'm using code from a Railscast :))

module DevelopmentMailInterceptor
  class DevelopmentMailInterceptor
    def self.delivering_email(message)
      message.subject = "intercepted for: #{message.to} #{message.subject}"
      message.to = "[email protected]"
    end
  end
end

works, but it doesn't load if I hadn't put the class inside a module.

Though this does not directly answer the question, but I think it is a good alternative to avoid the question altogether.

To avoid all the autoload_paths or eager_load_paths hassle, create a "lib" or a "misc" directory under "app" directory. Place codes as you would normally do in there, and Rails will load files just like how it will load (and reload) model files.