From: Jamis Buck <jamis@37signals.com>
Date: 2005-05-24T05:21:06+09:00
Subject: Re: Array.=== Bug, Rails Bug, or brain failure?

Markus,

when x.has_many :y, the :y property is not an array. It's an object  
that walks and talks like an array. (Just try using x.y.find  
sometime--it doesn't work like the Array version, which bit me hard  
several times in the past.)

If you _need_ it to be an array, you can do x.y.to_a. Otherwise, it's  
all about duck typing. :)

- Jamis

On May 23, 2005, at 2:04 PM, Markus wrote:

> I've got some rails code that is failing in a very strange way.  It is
> quite repeatable in situ, but I have yet to formulate a simple
> explanation of when it fails.
>
> Consider this code:
>
>     case x
>        when Array
>           print "Array\n"
>        else
>           print "Bogus\n" if x.is_a? Array
>        end
>
> Should it ever print "Bogus\n"?  I wouldn't think so, but when x  
> is  the
> Array returned by main_record.sub_records (where main_record is linked
> to sub_records by a "has_many :sub_record") it does.
>
> The class of x is "Array" and (obviously) "x.is_a? Array" but  
> "Array ===
> x" returns false.  It works for hand made arrays, the Array  
> returned by
> "SubRecord.find_all_by_main_record(main_record.id)"--which should be
> identical.
>
> I've only found one place in the whole codebase (in activerecord)  
> where
> === is redefined, and then only for active records themselves, not for
> the class, and certainly not for Class. In any case, it "redefines" it
> as "other.is_a?(self)", which is what I'd expect class to do.
>
> Adding:
>
> class Array
>     def self.===(other)
>         other.is_a? self
>         end
>     end
>
> right above the code in question fixes it.
>
> Has anyone else seen this? Did the semantics change when I wasn't
> looking?  Or is there a bug somewhere?  Or am I missing something  
> subtly
> obvious?
>
> --MarkusQ
>
>
>
>
>