Ghost in the machine

Fri, 20 Apr 2007 10:24:40 +0100

Yesterday in trying to debug a problem in our application I came across a very odd situation indeed. An object was failing to save somewhere in a chain of associations. After some rather painful debugging (made bearable only by Kent Sibilev's excellent ruby-debug package) I found the culprit.

Somehow an object o had sprung into being such that:

o.nil?
=> false

o.class
=> nil

o.object_id
=> nil

How can such a ghostly apparition come to be? It is possible to create on deliberately... redefining the class and object_id methods to return nil for example. But it's hard to see how such an object can occur naturally. Has anyone seen such a thing?

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Ghost in the machine