From: Dave Birch <thisisdaveb@...>
Date: 2009-05-17T04:32:32+09:00
Subject: BigDecimal singletons

Hi,

I'm a ruby nuby and I'm confused about something.  When I try to create
a singleton method for a BigDecimal like so:

require 'bigdecimal'
d = BigDecimal.new('10')

class << d
  def value
    32
  end
end

p.value

I get an error:
singtest.rb:7:in `singleton_method_added': can't define singleton method
"value" for BigDecimal (TypeError)

Doing this through IRB, I was surprised that if I then ran...

d.singleton_methods.sort

...after getting the error above, I get "value" listed as a singleton
method, and indeed, d.value yields 32.

If I wrap the singleton method definition in a begin...rescue block, the
TypeError is caught and not displayed, and the singleton method is
accessible.

If I replace d = BigDecimal.new('10') with d = String.new('10'), but
leave the rest of the code the same, I don't get the error and the
singleton method works as expected.  Is there something simple I'm
missing?

Thanks in advance...

Dave
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