From: "Bennett, Patrick" <Patrick.Bennett@...>
Date: 2002-08-13T05:22:28+09:00
Subject: RE: Q) about singleton methods and access control

This is what I'd "like" to do:
class A

  def initialize()
     @varInternalOnly = 'test'
   end
  
  def A.createSpecialA()
      testObj = A.new
      testObj.internalHelperMethod()	#  [Fails because internalHelperMethod is private - even though this is a class A method.  :\]
      return testObj
  end

private    
    def internalHelperMethod()
       @varInternalOnly = 'foo'
    end
end

   
A.createSpecialA()

I would like to have my singleton methods (like in C++) have access to protected/private members of its own class.  Without this, it's not possible to have static (singleton) class methods
act as helpers (or in my case, alternative constructors) and access 'private' methods/variables of its own class type.  To me at least, this reduces the usability of the access-control modifiers quite a bit.


-----Original Message-----
From: Christoph [mailto:chr_news@gmx.net]
Sent: Monday, August 12, 2002 3:09 PM
To: ruby-talk ML
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