From: Robert Klemme <shortcutter@...>
Date: 2006-07-09T18:30:09+09:00
Subject: Re: calling a method for an object in a .each block cont./chat

william robb wrote:
> Robert Klemme wrote:
> [ .. snip ..]
> 
> Thanks for the explanation.  I am a bit hazy on what is getting returned 
> and displayed in irb, but the structure of oo is comming clearer.  I was 
> simply returning a string from the #show method, and letting irb do the 
> actual 'display', which explaned what was happening.

Right.

>>>  Been
>>> programming in procedural languages since fortran 77, so this OO stuff
>>> is a bit mind bending.  But ... I like it!
>> Yeah, it took me some while to grasp it when I learned OO (Turbo
>> Pascal at that time).  But the OO paradigm is much stronger than plain
>> procedural code IMHO.
>>
> 
> The origional Turbo Pascal?  That came on one 5 1/4 inch diskette, the 
> first IDE I'd ever seen?  That wasen't OO, that was stright-up pascal, 
> no?

V 5.5 was OO - I'm not sure whether that was the first OO version.

> I guess you could call VBA/Excel OO, I've messed around with that, but 
> don't like it all that much.  OK to scrap out stuff, automate a chart 
> for a client or something ... but I can't stand all the 
> 'clickey-clickey' windows interface you have to plow through just to put 
> in a bit of code.

:-))

> But, enough chat.  I am really interested in what you are saying below. 
> I had a vauge notion to do this, but couldn't develop the syntax to 
> express what I wanted.  If you wouldn't mind, I would appreciate an 
> example or two.
> 
>> You could for example create individual classes for suit, face and
>> maybe also for value implementing the enum pattern, so you end up
>> having just a single instance for hearts, clubs, face_up, face_down
>> etc.

# poor mans enum pattern,
# for others see the RAA

Suit = Struct.new :name

class Suit
   VALUES = [
     HEARTS = new("Heart").freeze,
     CLUBS = new("Clubs").freeze,
     DIAMONDS = new("Diamonds").freeze,
     SPADES = new("Spades").freeze,
   ].freeze

   def to_s() name end

   def self.from_string(s)
     VALUES.detect {|su| s == su.name}
   end

   # restrict to the 4 instances created above
   def self.new(*a,&b) raise "Not allowed" end
end

Now you can do
Suit::HEARTS
Suit::VALUES.each {|s| puts s}
Suit.from_string "Hearts"
etc.

And also

case x.suit
   when Suit::HEARTS
     then puts "doing something with hearts..."
   when Suit::CLUBS
....
end

Kind regards

	robert