My Secret Life as a Spaghetti Coder
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My vocabulary is failing me right now. What do you call it when a piece of code checks the type of an object before doing something to it?

Type Casing is the act of using case statements in a program to determine what to do with an object based on what type of object it is. It's an OO fail, often hoping to implement Multiple Dispatch. (See also Case Statements Considered Harmful)

Here are three passive-aggressive ways to feel like you're getting back at typecasers.

The first tactic turns your object into an everything, so it's whatever the typecaser was looking for. I've called it OmniObject.

module OmniObject
  def is_a?(*)
    true
  end

  def kind_of?(*)
    true
  end
 
  def nil?
    true
  end
end

foo = "hello, world!"
foo.extend OmniObject
puts "Is foo a Fixnum? #{foo.is_a?(Fixnum) ? 'yes' : 'no'}"
puts "Is foo a Kernel? #{foo.is_a?(Kernel) ? 'yes' : 'no'}"
puts "Is foo a NilClass? #{foo.kind_of?(NilClass) ? 'yes' : 'no'}"
puts "foo.nil? => #{foo.nil?}"

The next one makes your object unable to decide what it is, turning it into a FickleTeenager. If he has to check more than once, the typecaser is going to have a tough time with a kid who can't make up his mind.

module FickleTeenager
  def is_a?(*)
    sorta
  end

  def kind_of?(*)
    sorta
  end
 
  def nil?
    sorta
  end
 
  def sorta
    truish
  end

  def truish
    rand < 0.5
  end
end

foo = "hello, world!"
foo.extend FickleTeenager
3.times{ puts "Is foo a String? #{foo.kind_of?(String) ? 'yes' : 'no'}"}

Finally, we have the AntisocialPrivacyAdvocate. When the typecaser asks him what he is, he tells them like it is: It's none of your damn business!

class WhatBusinessOfItIsYoursError < StandardError; end;
module AntisocialPrivacyAdvocate
  def is_a?(*)
    raise  WhatBusinessOfItIsYoursError
  end

  def kind_of?(*)
    is_a?
  end
 
  def nil?
    is_a?(NilClass)
  end
end

foo = "hello, world!"
foo.extend AntisocialPrivacyAdvocate
result = foo.kind_of?(String) rescue "#{$!} OMG, How Rude!"
puts result


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Comments
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Good stuff -- I literally laughed out loud (as opposed to just LOL). I do believe my favorite is the fickle teenager, but the antisocial module might actually be productive

Posted by Jesse Wolgamott on Dec 21, 2011 at 09:02 AM UTC - 5 hrs

Thanks!

I kind of like seeing a program halt and print out a stack trace that looks like this:

whatbusiness.rb:25:in `is_a?': WhatBusinessOfItIsYoursError (WhatBusinessOfItIsYoursError)
from whatbusiness.rb:29:in `kind_of?'
from whatbusiness.rb:39:in `<main>'


Of course I suppose you could rescue WhatBusinessOfItIsYoursError, extend OmniObject and retry. =)

Or if you really wanted to get fancy: rescue, find 3rd method in the stack trace, and rewrite it on the fly.

Posted by Sammy Larbi on Dec 21, 2011 at 09:54 AM UTC - 5 hrs

I call it chicken typing

http://talklikeaduck.denhaven2.com/2007/10/22/chic...

Posted by Rick DeNatale on Dec 23, 2011 at 12:10 AM UTC - 5 hrs

Thanks Rick, great name for it!

Posted by Sammy Larbi on Jan 09, 2012 at 12:14 PM UTC - 5 hrs

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