Loading a fixture clobbers a global variable

Rails
1

I’m making use of a global variable to do dynamic scoping in my models.
For example, here is how one model is defined:

class Invitation < ActiveRecord::Base
belongs_to :site

Scope all find calls to the current site_id.

scoped_methods << {
:find => { :conditions => [ ‘site_id = ?’,
$site_id ] }
}
end

In my ApplicationController, $site_id is set in a before_filter which
determines which subdomain the request came from. With this, I can
perform finds on my models without having to pass in the site_id every
time. This works well, although I understand it violates the MVC
philosophy - please bear with me.

It works well, except for tests. Actually, it works in tests if I
manually set $site_id, but only if I am not loading a fixture for
this model. For example, the following actually works (note that my
fixtures are commented out):

require File.dirname(FILE) + ‘/…/test_helper’

class InvitationTest < Test::Unit::TestCase
#fixtures :invitations

def test_global_wierdness
$site_id = 1

i = Invitation.find_by_last_name("Jones")
assert_valid i

end
end

So, if I run this test and watch my test.log file, I can verify that the
SQL query is run with site_id=1. All is good.

However, if I uncomment the fixtures line and watch my test.log file, I
find that $site_id is no longer visible within the model and my SQL
query ends up searching for site_id=NULL.

What exactly is going on here? Does loading a fixture somehow clobber
global variables? I’ve tried renaming the global $site_id to something
different (since that’s also a field in my Invitations table) but that
makes no difference.

Also, I can load fixtures for other models and the global variable
still works. It’s only when I load a fixture for the Invitation model
that it disappears.

I’ve been struggling with this problem for many hours and would be
greatly indebted to anyone who could educate me.

Thanks,

Scott

2

On 1 Oct 2007, at 22:49, Scott Garman wrote:

What exactly is going on here? Does loading a fixture somehow clobber
global variables? I’ve tried renaming the global $site_id to something
different (since that’s also a field in my Invitations table) but that
makes no difference.

Rails overrides the setup method, and this is where the fixtures are
loaded (ie before the code in test_global_weirdness runs). This
causes invitation.rb to be loaded. At this point $site_id is not set
and so when scoped_methods << {:find => { :conditions => [ ‘site_id
= ?’,$site_id ] } } is evaluated, $site_id is nil.
If you don’t have invitations as a fixture, then invitation.rb is
only loaded when Invitation is used, i.e. after you’ve set $site_id.
So it’s not that fixtures are clobbering anything. You’ll also have
problems if different tests try to set $site_id to different values.
Fundamentally this approach seems unwise. If you absolutely had to,
you could set $site_id in test_helper.rb

Fred

3

Frederick C. wrote:

Rails overrides the setup method, and this is where the fixtures are
loaded (ie before the code in test_global_weirdness runs). This
causes invitation.rb to be loaded. At this point $site_id is not set
and so when scoped_methods << {:find => { :conditions => [ ‘site_id
= ?’,$site_id ] } } is evaluated, $site_id is nil.

Fred, I can’t thank you enough for such a clear explanation. I’m
evaluating other ways of scoping my models, but you’ve resolved this
particular mystery.

Thanks,

Scott