From: Shea Martin <shea@...>
Date: 2007-01-06T06:40:12+09:00
Subject: cloning object with array members

Consider a simple class like this:
class MyClass
   def initialize
     @var1 = ''
     @arr1 = []
   end
end


Now if I have an instance of MyClass, and want to clone it, what is the 
'cleanest' way to do this?

a = MyClass.new
b = a.clone

This method leaves 'b.arr1' pointing to the same data as a.arr1.

Hmmm... I'll try overriding clone, and manually deal with the arrays:

def clone
   rslt = super.clone
end

This blows the stack, I believe because all methods are inherited virtually.

Ok, so now I have to manually copy everything in clone, whatever, I am 
getting sick of this:

   def clone
     rslt = MyClass.new
     rslt.var1 = @var1
     rslt.arr1 = @arr1.clone
     rslt
   end

Turns out this does not compute either, as there is no method var1= or 
arr1= ! I want to keep var1 private, so can't go this route either.


One more attempt:
   def clone
     rslt = MyClass.new

     self.instance_variables.each do |member|
       rslt.instance_variable_set( member, 
self.instance_variable_get(member).clone )
     end
   end

This fails as the methos do not seem to copy over.

There has to be a simple way to do something like this?  What is common 
recipe for something like this?   Should this really be that hard in ruby?

~S