From: Ian Macdonald <ian@...>
Date: 2002-04-26T11:48:28+09:00
Subject: how to check for unitialised class variable?

Hi,

Observe the following:

irb(main):006:0> class Foo
irb(main):007:1>   def initialize
irb(main):008:2>     @@foo ||= true
irb(main):009:2>   end
irb(main):010:1> end
nil
irb(main):011:0> bar = Foo.new
NameError: uninitialized class variable @@foo in Foo
        from (irb):8:in `initialize'
        from (irb):11:in `new'
        from (irb):11

The ||= (only assign if nil) assignment operator must necessarily
check for an existing value of @@foo and, if there isn't one, the
above error ensues.

How should one rewrite the above code? The objective is to avoid
reassignment of @@foo, once it has been defined.

Ian
-- 
Ian Macdonald               | The price one pays for pursuing any
ian@caliban.org             | profession, or calling, is an intimate
                            | knowledge of its ugly side.   -- James
                            | Baldwin 
                            |