From: Jason Lillywhite <jason.lillywhite@...>
Date: 2009-08-21T00:49:03+09:00
Subject: extending ruby - handling errors

I want to raise an ArgumentError, "Function only takes numeric objects."
if a non-numeric argument is passed to the existing Ruby method,
Numeric.ceil.

#Here is my feeble attempt to extend Ruby:

irb(main):001:0> class Numeric
irb(main):002:1>   alias :old_ceil :ceil
irb(main):003:1>   def ceil
irb(main):004:2>     raise ArgumentError,
irb(main):005:2*       "function only takes numeric objects." unless
self.is_a? Numeric
irb(main):006:2>     self.old_ceil
irb(main):007:2>   end
irb(main):008:1> end
=> nil

#But that does not work - I can't get past the call on the object

irb(main):009:0> "foo".ceil
NoMethodError: undefined method `ceil' for "foo":String
        from (irb):9

Could someone point me in the right direction? Thank you.
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