From: Luke Kanies <luke@...>
Date: 2006-08-02T08:03:22+09:00
Subject: Re: Strategies for autoloading ruby files

ara.t.howard@noaa.gov wrote:
> 
> this may be helpful (or not!  ;-))
> 
>   http://codeforpeople.com/lib/ruby/dynaload/

Clearly, I should always check your codebase before asking any questions. :)

> i use it for plugins in my satellite processing system like so
> 
> 
>   class PlugIn
>     def self.inherited other
>       Dynaload::export self, 'plugin' => true
>     end
>   end
> 
> 
> then plugins are written something like
> 
> 
>   require 'plugin'
> 
>   class MyPlugIn < Plugin
>     #
>     # stuff
>     #
>   end
> 
> 
> then, assume that is saved in myplugin.rb, then i can do
> 
> 
>   require 'dynaload'
> 
>   loaded = Dynaload::dynaload 'myplugin.rb'
> 
>   plugins = loaded.select{|klass, attributes| attributes['plugin'] == true}
> 
> 
> make sense?

Yeah.  Half of my question, though, was figuring out which files to 
load, although that's easy enough to resolve, I guess.  I'm assuming it 
does get moderately expensive as I do more of these, but I normally load 
by name (e.g., look for 'puppet/type/package/dpkg.rb' anywhere in the 
search path), and only sometimes load all files in all search directories.

I started out using the self.inherited method for all of this kind of 
work, but it just got too cumbersome eventually, at least partially 
because the object passed to 'inherited' has not yet been initialized. 
That is, with the following code:

   class MyClass < ParentClass
     @name = :myclass
   end

When 'inherited' is called, '@name' is not set, so you have to stick it 
in an array and then do shenanigans later to make it act like a hash. 
This is clearly a trivial example, because 'name' can (usually) be 
autodetermined from the class name, but you also can't test whether 
methods are defined, for instance.  With the 'new<thing>' methods, I can 
do any initialization on the class that I want (e.g., setting @name 
using accessor methods), class_eval the passed block, and then do any 
analysis I need.  See [1].

When I switched from using inherited to creating 'new<thing>' methods, 
it unleashed a flood of productivity.  I was astounded -- I barely slept 
for two weeks because so much was suddenly so easy when it had been so 
difficult for so long.

1 - 
http://reductivelabs.com/downloads/puppet/apidocs/classes/Puppet/Type.html#M000597

Notice all of the other 'new*' methods around this one.  I use it 
everywhere and I love it.

-- 
Neonle will continue to be rude, and will nretend that you had a small
stroke which makes you unable to say or see the letter "n".  Stunid
nractical joke, if you ask me.  Bunch of noon-heads, huh?
                 -- Fred Barling, Humorscope
---------------------------------------------------------------------
Luke Kanies | http://reductivelabs.com | http://madstop.com