From: Ian Macdonald <ian@...>
Date: 2004-02-09T12:03:30+09:00
Subject: === confusion

Hello,

After a couple of years of Ruby programming, I find that the ===
operator still has the ability to occasionally confound me.

Today, I had some code that looked like this:

foo = case bar.class
      when Foo::Bar
        'abc'
      when Foo::Bar::Baz
        'def'
      when Foo::Qux
        'ghi'
      else
        'jkl'
      end

The problem is that most comparisons of bar.class fell through to the
else clause. A quick debugging session on a particular instance of 'bar'
revealed that 'bar.class == Foo::Bar' was true, but
'bar.class === Foo::Bar' was false. Quite honestly, I don't understand
why, as I'm not overriding === anywhere. My classes are not derived from
any standard Ruby classes, either, so they should be inheriting ===
from Object, if I understand things correctly.

I fixed it by changing the start of the case statement to
'case bar.class.to_s' and then comparing to strings instead of object
identifiers, but I would like to understand what exactly === was doing
in the original case.

Ian
-- 
Ian Macdonald               | When neither their poverty nor their honor 
System Administrator        | is touched, the majority of men live
ian@caliban.org             | content.   -- Niccolo Machiavelli 
http://www.caliban.org      | 
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