From: Barun Singh <barunio@...>
Date: 2009-02-09T04:11:08+09:00
Subject: best way to protect class instance variables

Suppose I generate a class instance variable and create an accessor
function for it as follows:

class MyClass
  @blah = [0,1]
  def self.blah
    @blah
  end
end

I would like to prevent any other piece of code from having any way of
changing the value of the class variable.  While the code above prevents
me from saying "MyClass.blah = 'hello'", it does allow me to say
"MyClass.blah[0] = 'hello'", which changes the value of the class
instance variable (to ['hello',1]) any time I try to access it in the
future.

I know that one way to fix this problem is to simple return a copy of
the instance variable instead of returning the instance variable itself,
by changing the accessor to:

def self.blah
  @blah.dup
end

This way, another piece of code is still able to say "MyClass.blah[0] =
'hello'", but it won't affect the results returned by "MyClass.blah" in
the future.

So this works for me, but I'm just wondering -- is there a better way to
do this?
-- 
Posted via http://www.ruby-forum.com/.