Rails - Apr 2008 - ActiveRecord models stored in globals lose methods

Hi all,

I was experimenting with storing models in Ruby''s global space (as a
quick and dirty alternative to memcached), and I came across some
weird behavior I couldn''t figure out.

First, I create a basic ActiveRecord model:

class Bob < ActiveRecord::Base
  def chunky; ''bacon''; end
end

Next, I write a controller that sticks the model in a global and calls
a method:

class TestController < ApplicationController
  def index
    $some_global ||= Bob.new
    render :inline => $some_global.chunky
  end
end

Then I start up a Mongrel via script/server and call the
TestController. The first time I do this, things go as expected: it
just spits out ''bacon''. The second time, however, I get a
NoMethodError saying $some_global doesn''t have a chunky method. I
checked $some_global''s class and depending on the method called, get
weird results:

$some_global.class  # => Bob
$some_global.is_a? Bob # => false

I also ran $some_global.methods, which prints out of the methods
associated with ActiveRecord (e.g. save and valid?) but no chunky.

This only appears to happen with models inheriting from ActiveRecord.
Removing ActiveRecord::Base from the inheritance chain seems to avoid
this problem.

Anyone have any ideas why this happens? Thanks!

-- Andrew
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On 13 Apr 2008, at 02:20, Andrew Fong wrote:
>
> I also ran $some_global.methods, which prints out of the methods
> associated with ActiveRecord (e.g. save and valid?) but no chunky.
>
> This only appears to happen with models inheriting from ActiveRecord.
> Removing ActiveRecord::Base from the inheritance chain seems to avoid
> this problem.
>
In development mode classes are reloaded on each request. The nitty  
gritty of how this is implemented essentially involves dismantelling  
your models and throwing them away. If you hang onto a class via a  
global variable or similar then you get the thrown away version of the  
class.

Fred
> Anyone have any ideas why this happens? Thanks!
>
> -- Andrew
> >

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