Rails - Feb 2008 - Object.subclasses_of(MyModel) not working in development environment

I''m trying to use the subclasses_of method but I''m getting
strange results.

The first request after I restart the server, everything works fine. Subsequent
requests return an empty array.

Can anyone shed any light on why this happens or what I can do about it?

Thanks,
Gareth


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On 21 Feb 2008, at 11:34, Gareth Adams wrote:
>
> I''m trying to use the subclasses_of method but I''m
getting strange
> results.
>
> The first request after I restart the server, everything works fine.  
> Subsequent
> requests return an empty array.
>
> Can anyone shed any light on why this happens or what I can do about  
> it?
This is probably to do with rails'' magic unloading of your classes  
after the request has run. Be aware that subclasses_of might not give  
you all your subclasses, because if the file hasn''t been loaded yet  
then subclasses_of won''t know about it.

Fred

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Frederick Cheung <frederick.cheung@...> writes:
> On 21 Feb 2008, at 11:34, Gareth Adams wrote:
> 
> > Can anyone shed any light on why this happens or what I can do about  
> > it?
> 
> This is probably to do with rails'' magic unloading of your classes
> after the request has run. Be aware that subclasses_of might not give  
> you all your subclasses, because if the file hasn''t been loaded
yet
> then subclasses_of won''t know about it.
Thanks, Fred,

I''m aware that not all models are loaded by default and I have a
Dir[...].each
{|f| require f} to make sure the relevant subclasses *are* loaded when I need to
access them.

I did know that Rails had some magic to let you see your updated models without
having to restart your server every request, but I''m still confused why
Ruby
doesn''t see these classes in subsequent requests. If they''re
unloaded at the end
of the request then surely they get *re*loaded the next time I need them -
that''s the point, isn''t it?

Gareth


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On 21 Feb 2008, at 12:19, Gareth Adams wrote:
>
> Frederick Cheung <frederick.cheung@...> writes:
>
>> On 21 Feb 2008, at 11:34, Gareth Adams wrote:
>>
>>> Can anyone shed any light on why this happens or what I can do
about
>>> it?
>>
>> This is probably to do with rails'' magic unloading of your
classes
>> after the request has run. Be aware that subclasses_of might not give
>> you all your subclasses, because if the file hasn''t been
loaded yet
>> then subclasses_of won''t know about it.
>
> Thanks, Fred,
>
> I''m aware that not all models are loaded by default and I have a  
> Dir[...].each
> {|f| require f} to make sure the relevant subclasses *are* loaded  
> when I need to
> access them.
>
> I did know that Rails had some magic to let you see your updated  
> models without
> having to restart your server every request, but I''m still
confused
> why Ruby
> doesn''t see these classes in subsequent requests. If
they''re
> unloaded at the end
> of the request then surely they get *re*loaded the next time I need  
> them -
> that''s the point, isn''t it?
One thing that does happen is that when rails unloads stuff, it  
essentially empties out existing classes. If you''re somehow hanging  
onto an old reference to MyModel and call subclasses_of on that then  
it''s possible that you''d get back an empty array

Fred

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