[ruby-talk:19699] class methods and optimizing

Does anyone know what class methods are as opposed to instance methods? Are 
they for optimizing? when would I use them?I have looked at a couple manuals 
that tell you how to do them: def classname.method but none seem to explain 
the why and when.

And this leads to my second question.  In terms of memory usage and speed, is 
it better to extend the existing classes (when possible) or to build your 
own, or to just make a subclass? e.g. If I program a deck routine for a card 
game I can just add shuffle, play etc. routines to class Array.  Now the 
computer isn't holding an extra class definition in memory, but ALL arrays 
(not decks) are also extended. If I make my own class/subclass, not all of 
the arrays are extended but there is another class definition in memory...

The first question is related to the second as well... what difference does 
it make if they are class methods... Programming Ruby says that they are 
methods that stay with the class in memory and not with the objects... does 
that mean that extending Array but making them class ones mean that all 
Arrays before that don't get those methods or what? hmmm.....

The last one here is easy... I remember from somewhere that self is the 
default object.  So can I remove it from class definitions completely and 
it's just there to save confusion while reading? (Sorry brain on the 
fritz....*bang* *bang*....)

My deck array extention (for those interested) is at 
http://www.rubycookbook.org/showrecipe.rb?recipeID=115

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Chris Moore

As a dog returns to it's vomit
so a fool totheir folly -God