From: John Carter <john.carter@...>
Date: 2006-05-29T10:36:55+09:00
Subject: SafeObject protection for standard gotcha's.

I have just noticed that my codeline has silent breakage all over the
place and I have an idea how to catch this sort of thing in future...

How it happened is this....

I had a variable "platform" that I used all over the place. It was a String.

Then it had to become substantially smarter, so I made it an object
instance of class Platform.

Unfortunately in quite a few places somehow I forgot to convert
   if platform == 'thisone'

to
   if platform.name == 'thisone'
   (or even better and simpler just....
      platform.doTheRightThing
   )


And...

Ruby silently accepted my mistake, threw no error and took the false branch.


So to catch that class of breakage I should do something like....

module PolymorphicallySafeObject
   def ==(object)
     raise "Strict Typing failure expected #{self.class} found #{object.class}" unless
       object.kind_of?( self.class) || self.kind_of?( object.class)
   end
end

class Platform < SomeThing
   include PolymorphicallySafeObject

.
.
.
.
end

Now it occurs to me this might be quite a useful trick.

For example catching failures to define an equal method if you define a hash method
and vice versa.

Question for the Group....
==========================

What other useful cross checks and gotchas catchers could I include in SafeObject?

For extra marks, come up with a DuckSafeObject.

John Carter                             Phone : (64)(3) 358 6639
Tait Electronics                        Fax   : (64)(3) 359 4632
PO Box 1645 Christchurch                Email : john.carter@tait.co.nz
New Zealand

Carter's Clarification of Murphy's Law.

"Things only ever go right so that they may go more spectacularly wrong later."

From this principle, all of life and physics may be deduced.