Ruby and object references / copying

[beatTheDevil]

Hey guys,

I had a theoretical question about Ruby's object handling. Not that it really matters, but I'm using Ruby 1.8.6.

In Ruby, every variable holds a reference to an object. For instance, if you were to say:

myVar1 = []
myVar2 = myVar1
myVar2 << "giggity giggity goo"
 
myVar[0]      # => "giggity giggity goo"
 

...the result is that the Array object referenced by both variables (it's the same object after all) would hold a new element.

However, this creates an interesting dilemma with regards to attribute readers, because technically, you can modify what should be a protected object. Normally this isn't a problem, but in the case that the object has mutating/destructive methods, they can be used. Consider the following class:

class Retarded
  attr_reader :var
 
  def initialize
    @var = "mystring \n"
  end
end
 
x = Retarded.new
 
x.var.chomp!     # => "mystring "
x.var            # => "mystring " the internal variable has changed
 

Is there any idiomatic way to avoid this problem, or do we all just live with it, hoping it won't matter in the end?

Thanks!

[improvcornartist]

I have noticed the same thing. I've had programs where I wanted to play with an array, but keep the original unchanged. What I had to do was make a clone (obj.clone) and then alter the clone object. This probably doesn't help much in the way of attribute readers, but you could make a make a method to return the clone so the original isn't touched. I am by no means an expert on Ruby (still fairly new to it), so this is just my understanding. I would be interested in what others have to say, also.