From: Eric Hodel <drbrain@...7.net>
Date: 2006-04-10T15:04:51+09:00
Subject: Re: ObjectSpace searching

On Apr 9, 2006, at 8:06 PM, Mark Alexander Friedgan wrote:

> I wrote some code that searches ObjectSpace prior to initializing an
> object to see if one of that type and some attributes is already
> present and uses that instead of initializing. (yes it's active record
> and i am trying to avoid stale object errors). How horrible is this? I
> am searching by specific class name so in practice it ends up looking
> at at most a couple of instances but is there something inherently
> wrong with doing this?
>
> def find_in_space(search_id, search_version = nil)
>   retval =  nil
>   ObjectSpace.each(Person){|person|
>       retval = person if (p.id == search_id) &&
>                                search_version &&
>                                p.lock_version == search_version
>   }
>   return retval || Person.find(search_id)
> end

For one, you could fail early:

s = 'foo'
obj = nil
ObjectSpace.each_object(String) { |str| if str.equal? s then obj =  
str; break; end }
p obj # => 'foo'

Really, you should handle errors properly.  This code won't eliminate  
the possibility of a double-update, another process can cause them to  
happen after this code gets run.

(Also, you should use cached_model and turn on its local cache.  Much  
more efficient than traversing ObjectSpace.)

-- 
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net
This implementation is HODEL-HASH-9600 compliant

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