Rails /lib modules and

Question

I am writing a custom wrapper for open_flash_chart plugin. It's placed in /lib and load it as a module in ApplicationController.

However, I have some Class hierarchy or smth problem.

From any controller I can access open_flash_chart functions as OpenFlashChart, Line etc

However, in a class in a /lib module, it doesnt work!

Any ideas?

Solution 1

There are two ways that files get loaded in Rails:

• It is registered in the autoload process, and you reference a constant that corresponds to the file name. For instance, if you have app/controllers/pages_controller.rb and reference PagesController, app/controllers/pages_controller.rb will automatically be loaded. This happens for a preset list of directories in the load path. This is a feature of Rails, and is not part of the normal Ruby load process.
• Files are explicitly required. If a file is required, Ruby looks through the entire list of paths in your load paths, and find the first case where the file you required is in the load path. You can see the entire load path by inspecting $LOAD_PATH (an alias for $:).

Since lib is in your load path, you have two options: either name your files with the same names as the constants, so Rails will automatically pick them up when you reference the constant in question, or explicitly require the module.

I also notice that you might be confused about another thing. ApplicationController is not the root object in the system. Observe:

module MyModule
  def im_awesome
    puts "#{self} is so awesome"
  end
end

class ApplicationController < ActionController::Base
  include MyModule
end

class AnotherClass
end

AnotherClass.new.im_awesome
# NoMethodError: undefined method `im_awesome' for #<AnotherClass:0x101208ad0>

You will need to include the module into whatever class you want to use it in.

class AnotherClass
  include MyModule
end

AnotherClass.new.im_awesome
# AnotherClass is so awesome

Of course, in order to be able to include the module in the first place, you'll need to have it available (using either of the techniques above).

Solution 2

In Rails 3 /lib modules are not loaded automatically.

This is because the line:

# config.autoload_paths += %W(#{config.root}/extras)

inside config/application.rb is commented.

You can try to uncomment this line or, (it worked even better for me), leave this commented (for future reference) and add this two lines:

config.autoload_paths += %W(#{config.root}/lib)
config.autoload_paths += Dir["#{config.root}/lib/**/"]

Solution 3

What worked for me, besides uncommenting config.autoload_paths (I’m on Rails 3.1.3), was to create a initializer like this:

#config/initializers/myapp_init.rb
require 'my_module'    
include MyModule

This way I can call mymodule methods from anywhere and as class methods Model.mymodule_method or as instance methods mymodel.mymodule_method

Maybe some expert may explain the implications of this. By now, use it at your own risk.

Edit: Afterwards, I think a better approuch would be:

create a initializer like this:

#config/initializers/myapp_init.rb
require ‘my_module’

Include the module where needed, like this:

1) if you want to use it as "Class Methods" use "extend":

class Myclass < ActiveRecord::Base
   extend MyModule
   def self.method1
      Myclass.my_module_method
   end
end

2) if you want to use it as "Instance Methods" include it inside Class definition:

class Myclass < ActiveRecord::Base
include MyModule
   def method1
      self.my_module_method 
   end
end

3) remember that include MyModule refers to a file my_module.rb in your load path that must be required first

Solution 4

To use the module lib/my_module.rb in your models and controllers:

In config/application.rb:

config.watchable_dirs['lib'] = [:rb]

In your model (similar idea for your controller):

require_dependency 'my_module'

class MyModel < ActiveRecord::Base
  include MyModule

  MyModule.some_method
end

This method is described in more detail at http://hakunin.com/rails3-load-paths

View more solutions

Comments

[Mike]

Just wanted to add : If one of your module in /lib (or in one of the autoload directories) is already define ; exemple you overload ActiveRecord or String, you'll have to explicitly require it or it won't be loaded

[mkirk]

strangely, I'm getting: uninitialized constant GaClient (NameError), unless I require 'ga_client' beforehand (the class is defined in lib/ga_client.rb). Is there documentation for the autoload naming scheme?

[jibiel]

This will duplicate ../lib path in ApplicationName::Application.config.autoload_paths array.

[ylluminate]

@jibiel so what's the resolution here?

[Mindaugas MG]

why did the latter option work better for you? Also, why was the default changed...there must be a reason despite lots of people finding work arounds.

[S.M.Mousavi]

I have created my module on lib folder, therefore i have added config.autoload_paths += %W(#{config.root}/lib) on config/application.rb file. After that i followed your suggestion to adding config/initializers/myapp_init.rb file and it's contents. Everything is good. Thanks a lot :)