From: Christoph <chr_news@...>
Date: 2002-08-13T05:08:37+09:00
Subject: Re: Q) about singleton methods and access control


"Patrick Bennett" wrote,
....

> Recently, I was rather surprised to learn that singleton methods aren't
> able to access protected/private members of a class.


Hm I not quite sure to what access problem you are
refering to. Could illustruted this in an example. Afaikt
every thing seems to be oaky - for example, I get the
output

---
"fine"
"fine"
"fine"
protected method `sometimes_fine' called for #<B:0x284ab10>
protected method `bad' called for #<B:0x284ab10>
me everything seems to be okay - for example
---

when running the the test script

---
# illustrate protected

class A
    def okay(x)           x.fine end
    def sometimes_okay(x) x.sometimes_fine end
    def never_okay(x)     x.bad end

    def sometimes_fine;   p "fine" end
    protected
    def fine;             p "fine" end
end

class B < A
  protected
  def bad
    p "bad"
  end
end

a = A.new
b = B.new

a.okay b

class << a
  def okay(x)
    x.fine
  end
end

a.okay b
a.sometimes_okay b

class << b
  protected
  def sometimes_fine
     super
  end
end

begin
  a.sometimes_okay b
rescue NameError => mes
  puts mes
end

begin
  a.never_okay b
rescue NameError => mes
  puts mes
end
---

> Unfortunately, I'd like to have a class with multiple singleton
> 'constructor' methods.  Each would return a new instance of the class,
> initialized properly.  None of these actions would really make sense to
> have in Initialize.
> Well, if the singleton method can't access protected/private
> members/methods of the class, then how can I have protected portions of
> the class (to avoid problems with normal users of the class), and still
have
> a signleton method create intiailized instances of the class?
>
> Hopefully I'm completely missing the boat on this one and there's a
> solution to my problem.

Hm, I am quite sure that this problem can be resolved (in the
worst case just use the "send(:name_of_private_method,*meth_args)
trick"- Again could illustrate your problem with a code example?


/Christoph