From: Robert Klemme <bob.news@...>
Date: 2006-02-16T23:38:28+09:00
Subject: Re: Private methods - only available to oneself?

David Vallner wrote:
> Also, a minor mental exercise just came to mind. Presuming Ruby
> private would work like in C++, consider this code snippet:
>
> class A
> def foo
> puts "foo"
> end
> private :foo
> end
>
> a = A.new
> b = A.new
>
> def b.bar
> foo
> end
>
> Should this be valid? Is b an instance of the same class as a? If
> not, should the call to #foo still be valid or not? (E.g. should we
> consider singleton classes in the method access rules?)

It's valid.  And it should be IMHO.

> On a slightly related note, in case people watching the thread aren't
> confused enough as it is: Ruby's private methods are actually
> accessible from subclasses.

.... and superclasses:

irb(main):001:0> class Base
irb(main):002:1> def foo() bar() end
irb(main):003:1> end
=> nil
irb(main):004:0> class Der < Base
irb(main):005:1> def bar() "bar!" end
irb(main):006:1> private :bar
irb(main):007:1> end
=> Der
irb(main):008:0> Der.new.foo
=> "bar!"
irb(main):009:0>

> In any case, I think determining anything based on the notion of "the
> same class" in Ruby would only lead to more ambiguity in the language
> rather than make it easier to comprehend.

The appropriate term when it comes to private methods is "the same
instance". :-)

> It would also seem very
> non-rubyish to me, since as opposed to the C++ language family, a
> class is not the only, or sometimes even not even an important
> element of defining an object's behaviour.

Definitely!

Kind regards

    robert