Rails custom class static init

Question

Given a class

# foo.rb
class Foo
  Rails.logger.info "Foo loaded"
end

located in #{Rails.root}/app/lib. I added to config/application.rb the following:

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

When I startup rails either via rails s or rails console, I would like to see Foo loaded being logged. This is a simplified version of what I am intending to do, but it adequately demonstrates what I am trying to achieve. Currently, what happens is that nothing is logged at startup. Then, when I explicity use Foo, for example with Foo.new, I see the message logged.

What is the most appropriate method in Rails 3 to accomplish this so I see the logged message at startup?

sorens · Accepted Answer · 2011-03-28 03:31:37Z

Here is what I ended up doing:

(1) In the class app/lib/foo.rb, i added a static method to require the appropriate files

def self.load_foos
  Dir["#{Rails.root}/app/lib/foos/*_foo.rb"].each do |file|
    require file
  end
end

(2) in foo.rb, I added a static method so that subclasses could register themselves

def self.register 
  if @@subclasses.include?( self.registration_symbol )
    raise FooExceptionSymbolAlreadyUsed, "symbol [#{self.registration_symbol}] is already in use."
  end
  @@subclasses[self.registration_symbol] = [self.registration_priority,self]
end

(3) I created a directory at app/lib/foos where in I put the various subclasses of foo and named them this_foo.rb and that_foo.rb.

(4) In the subclass app/lib/foos/this_foo.rb, I added the following

class Foos::ThisFoo < Foo

  def self.registration_symbol
    :this
  end

  def self.registration_priority
    100
  end

  # other methods removed to make example easier to read

  register
end

(5) I added a config/initializers/load_foos.rb which simply had

Foo::load_foos

Any subclass of Foo that I put in app/lib/foos/ and name correctly, will automatically be loaded at startup. Each subclass overrides and implements the methods for registration_symbol and registration_priority (the priority is used later to sort an enumeration) and the symbol is used in a create method.

Thus, I can publish a spec to my developers that shows them which methods of Foo to implement in their subclasses and how to register it and where to save it and then the Rails application will automatically load those files on the next startup.

Xavier Holt · Accepted Answer · 2011-03-25 01:02:30Z

0

I had a similar situation - I had a whole bunch of constants in my models that really only needed to be loaded once, when Rails started, but seemed to be getting reloaded every time I accessed that model. I solved it as follows:

I defined the constants in a file in config/initiaizers (files there are loaded automatically at startup)
I added methods to my models that accessed those constants

If you're dealing with constants (e.g. Foo::PI = 42), this should work for you. If you're defining methods... maybe? You might run into some problems in development mode, when Rails reloads classes that have changed - I'm not sure.

Hope this helps!

answered Mar 25, 2011 at 1:02

Xavier Holt

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1 Comment

sorens Over a year ago

I am looking to use methods. config/initializers was one of the methods I had been considering. Just looking to see if that is the appropriate manner to solve this or if there was something different/better. thanks for the answer.

Alan Peabody · Accepted Answer · 2011-03-25 01:49:26Z

0

The Rails development environment, while wonderful for developing, is a bit odd about loading and requiring.

However, if you use a standard Ruby require you will find things more predictable. I would suggest you leave as much as possible using the rails config.autoload_paths

For the code you want to always require, just add a require 'app/lib/foo' at the very end of your config/application.rb, outside the module definition.

Also, typically lib is at the root of the rails directory, not in the app folder. Was that a type or a conscious choice?

answered Mar 25, 2011 at 1:49

Alan Peabody

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1 Comment

sorens Over a year ago

Yes, there is a lib directory in the Rails.root. The 'lib/ in my example could have easily been squishy_banana_gold/ except lib/ was quicker to type. thanks for the answer.

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