Re: Strategies for autoloading ruby files

On Wed, 2 Aug 2006, Luke Kanies wrote:

Hi all,

Following up on my post about complicated problems, here's a much simpler
problem that I need to tackle.

There are many parts of my framework that are extensible, and I want people
to be able to create extensions without modifying the core framework, akin
to how you don't have to specifically load each model and controller in
Rails.

Is there a relatively standard way of doing that with Ruby? This is what
I'm doing in one of my projects, Facter[1]:

# Now see if we can find any other facts
$:.each do |dir|
fdir = File.join(dir, "facter")
if FileTest.exists?(fdir) and FileTest.directory?(fdir)
Dir.glob("#{fdir}/*.rb").each do |file|
# Load here, rather than require, because otherwise
# the facts won't get reloaded if someone calls
# "loadfacts". Really only important in testing,
# but, well, it's important in testing.
begin
load file
rescue => detail
warn "Could not load %s: %s" %
[file, detail]
end
end
end
end

I've tried further copying Rails by checking that loaded files create the
objects it seems they should create (e.g., here they should create a fact
named after the file), but users constantly complained about those warnings.

Is this the best way? Any other recommended mechanisms?

I'd actually like the autoloading to work either on-demand (e.g., look for 'facter/myfact' if I ask for the 'myfact' fact), or load all of them right now.

Hmm. In fact, it'd be ideal if you could write a module that allows you to register autoload paths (e.g., I'd use 'facter', 'puppet/type', 'puppet/type/package', 'puppet/type/service', and lots more), and then just have hooks into that module so that you could autoload all instances, or just load a specific name.

1 - http://reductivelabs.com/projects/facter

this may be helpful (or not! ;-))

http://codeforpeople.com/lib/ruby/dynaload/

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?

the reason it's at 0.0.0 is that it just worked for me - been using in
production for a long time.

cheers.

-a
--
we can never obtain peace in the outer world until we make peace with
ourselves.
- h.h. the 14th dali lama

.

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