From: Lionel Thiry <lthiryidontwantspam@...>
Date: 2005-04-15T06:24:39+09:00
Subject: Re: class locals as class methods

Trans a �crit :
> So I find myself once again creating some classes that have
> attributes/state. I have two options, either the class defines
> a class method for the info, or in a superclass I define a method
> that will set that info to a class var when called.
> 
>   # Example A
>   class Thing1 < TheseThings
>     def self.mystate ; "what have you" ;  end
>   end
> 
> or
> 
>   # Example B
>   class Thing1 < TheseThings
>     mystate "what have you"
>   end
> 


You can use the attr_* instead:

  class Thing1 < TheseThings
   class <<self
    attr_accessor :mystate
   end
  end



> The first is rather, well, ugly. Although it makes sense, it's
> what one does at the instance level all the time (i.e. defining
> methods to fit the interface). The second is nice and dsl-ish,
> but requires a method to be predefined in TheseThings which
> actually creates a number of oddities, like how does one read
> the info out, and still be able to set it to nil? If that's an
> issue one is lead to instead define two class methods, and
> having to use self.maystate = "blah blah", instead.
> 
> Now everytime I go about this kind of thing I actually find
> myself writing:
> 
>   # Example C
>   class Thing1 < TheseThings
>     mystate = "what have you"
>   end
> 
> as that just feels natural. But then I have to go back and fix
> it, of course. So last night it hits me, why not? Why not have
> class locals define class methods? So in this case, Example C
> would basically be like doing Example A.

That's actually how python works.

class Thing1(TheseThings):
	my_state = "what have you"
print Thing1.my_state # output: what have you

Well, it doesn't really create a my_state method, and doesn't really create some 
@my_state anywhere. But at use, it works the same as you'd want ruby to work.

> Yes, I know there's
> namespace overlap, but class locals are rare enough that I don't
> think that's a show stopper. Maybe there are  other problems I'm
> not seeing, perhaps there's some OOP formalism that this rubs the
> wrong way.

I haven't the ability to demonstrate you anything, but my intuition is that it 
is not much adequate for ruby...

> I don't know. But I've given it more than "15 minutes"
> and it's actually growing on me. Am I crazy?

Crazy of wanting ruby to look like python? Err... ;)

--
Lionel Thiry