From: Christoph <chr_mail@...>
Date: 2003-12-01T02:00:53+09:00
Subject: Re: Class-level readers and writers

David A. Black wrote:
...
> What you're describing is a similarity, not a connection :-) 

I am not in the position to argue about fine point of the English
language with you, but a similarity is a "kind_of" (in the OO
sense) a connection in my orthographically challenged book:-) 

> What I mean is that there's no interdependency, conceptually 
> or in implementation, between class vars and class instance 
> vars.  People look for connections in trying to understand 
> them, but they're actually best understood separately.

Maybe you right about the latter point - I just don't know ...

> 
> As for the new-style class variables compares with 
> traditional accessors defined on the Class object: the main 
> difference I see is that the accessors are presumably 
> callable by anyone, whereas the new class vars will be 
> class-local (including instance method definitions).  It's 

You can  can achieve the same effect  by declaring the
class accessor methods (the instance version) protected

class A
	__var__ = nil
	protected
	define_method(:var) {|| __var__ }
	define_method(:var=) {|rhs| __var__= rhs }
       ...
end

Also I would not mind the introduction of ``class_protected'' 
visibility attribute for class methods.  Of course, it is bit of a
contradiction to champion an extra access modifier in order
to simplify visibility rules:-)

Example: Given declaration

class A; end
class B < A
    def self.meth
	puts "okay"
   end
   class_protected :meth
end

class B
   def m
	B.meth
  end
End

class A
   def foo
	B.meth
   end
end


B.new.foo # okay
A.new.foo # NoMethodError - called class protected ...

...

/Christoph