Q) about singleton methods and access control

ruby-talk
1

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

Thanks,
Patrick Bennett

2

“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