Auto-loading lib files in Rails 4

Question

I use the following line in an initializer to autoload code in my /lib directory during development:

config/initializers/custom.rb:

RELOAD_LIBS = Dir[Rails.root + 'lib/**/*.rb'] if Rails.env.development?

(from Rails 3 Quicktip: Auto reload lib folders in development mode)

It works great, but it's too inefficient to use in production- Instead of loading libs on each request, I just want to load them on start up. The same blog has another article describing how to do this:

config/application.rb:

# Custom directories with classes and modules you want to be autoloadable.
config.autoload_paths += %W(#{config.root}/lib)
config.autoload_paths += Dir["#{config.root}/lib/**/"]

However, when I switch to that, even in development, I get NoMethodErrors when trying to use the lib functions.

Example of one of my lib files:

lib/extensions.rb:

Time.class_eval do
  def self.milli_stamp
    Time.now.strftime('%Y%m%d%H%M%S%L').to_i
  end
end

Calling Time.milli_stamp will throw NoMethodError

I realize others have answered similar questions on SO but they all seem to deal with naming conventions and other issues that I didn't to have to worry about before- My lib classes already worked for per-request loading, I just want to change it to per-startup loading. What's the right way to do this?

Uund

Is the config/initializers folder automatically loaded when a Rails app starts up? – Boggle

Answer 1

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.

Conakry

@ifyouseewendy- You're exactly right- because extensions.rb wasn't following the Rails naming conventions, Rails wouldn't include it in the loading process. I got it working by manually requiring it. – Uund

@Conakry how can I include files before models are loaded? add the path to autoload it's cool, but how control the order of inclusion? thx – Tannate

@Tannate "include files before models are loaded", you may manually require your file without using autoload feature. – Conakry

@Conakry if I require it in initializer but the file are in autoload_path, it will be reloaded (loaded 2 times) or not? theire is a "require_once" like in php? – Tannate

@Tannate nope, and why you manually require and add to autoload_path, what's the situation? – Conakry

@Conakry I whant include all files in special folder in "app/", but, I don't want require it one by one, so I add the folder to the path, but certain files have to be include before models to works, so I have a problem^^ – Tannate

@Tannate Got it, I think you may add these certain files to eager_load_paths, which Rails will eager load on boot. – Conakry

@Conakry the problem to this solution is it's loaded only at server start, if I want change data, I have to relaod server, I need a solution with no interuption of service... reloaded each time. – Tannate

@Tannate Set config.cache_classes = false which is default in development env, which makes Rails reload classes and modules on each reqeust. – Conakry

@Conakry If I have files under lib/dir1/dir2/foo.rb , your solution doesn't load them on start.. I am in 4.2 – Djerba

This doesn't seem to work in Rails 5 API in production (but does in development). I believe that you need to use config.eager_load_paths << Rails.root.join('lib'). However, that has a major downside in that eager_load_paths loads everything in tasks as well. I think that lulalala's solution is better. Here's a blog post with more details: blog.arkency.com/2014/11/… – Boycie

I'm getting a can't modify frozen Array error when appending to config.autoload_paths << in Rails 5.1. This question has the error and solution: https://mcmap.net/q/119791/-can-39-t-modify-frozen-array-typeerror-config-application-rb-42-in-lt-lt-39. You need to use concatenation config.autoload_paths +=. – Fraunhofer

Answer 2

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.

Hospers

I am in Rails 4.2. and it doesn't auto load files under app, I need to do it manually......or need to put it in the autload path.. – Djerba

You are wrong, Arup, any subdirectories of app directory are automatically in the autoload_paths array in Rails 4.2.See edgeguides.rubyonrails.org/… – Sedimentation

Excepting the app/views directory which does not get added; or rather gets explicitly removed. – Supplant

Great answer. Only thing that worked for me on rails 5/api. – Stereotomy

Just remember that lib is meant for code that can be applied to multiple projects and might possibly be extracted to a gem. If not create a more appropriate folder under app search as services/ or presenters/ and even subdirs off these. – Cardew

Will have to move dir under app folder to auto load in Rails 5. Just adding the GitHub Discussion Link for reference. – Beals

Answer 3

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.

Constipate

In ruby "matching appropriately" means that the file is located in the file system at LOAD_PATH/module/class.rb (underscored) where LOAD_PATH is in the load paths used by the Ruby app (autoload_paths in the case of Rails). lib has fluctuated from being auto loaded by Rails to not being autoloaded, and in recent versions (>= Rails 3.x) it is not autoloaded. Whatever magic is making this work for you is not recommended. Perhaps it is an old Railscast? – Statistical

Answer 4

Use config.to_prepare to load you monkey patches/extensions for every request in development mode.

config.to_prepare do |action_dispatcher|
 # More importantly, will run upon every request in development, but only once (during boot-up) in production and test.
 Rails.logger.info "\n--- Loading extensions for #{self.class} "
 Dir.glob("#{Rails.root}/lib/extensions/**/*.rb").sort.each do |entry|
   Rails.logger.info "Loading extension(s): #{entry}"
   require_dependency "#{entry}"
 end
 Rails.logger.info "--- Loaded extensions for #{self.class}\n"

end

Selfabnegation