Copying via .dup

[khmp]

I have a question in which I first scoured the web for an answer, to no avail. I'm attempting to copy an object which I thought simple enough to do. So I'm trying to use .dup/.clone/= and it copies and all but whatever alteration I make to the duplicate the original is also altered. I guess they both reference the same memory. The question I have is how do I create a copy and have it be new memory? Do I have to write a method that acts as a copy constructor for the object?

Thanks for taking the time to read my problem! :thumb:

 

[Zeriab]

Both .dup and .clone returns a shallow copy.
Here is a code snippet which should increase your knowledge what is meant with a shallow copy:

class IntegerContainer
  attr_accessor :integer
  def initialize(value=0)
    self.integer = value
  end
  def inspect
    return integer.to_s
  end
end

a = IntegerContainer.new
b = IntegerContainer.new(2)
c = IntegerContainer.new(5)
d = IntegerContainer.new(-6)
array = [a,b,c]
p array
array2 = array.dup

array2 << d

p array, array2

array[1].integer += 10

p array, array2

If you have questions to this code please do ask ^_^

 

[khmp]

The problem is the shallow copy with using some simpler objects the behavior is as expected. But what I was trying to copy was a Game_Map. So the code I had was the following:

  ...
  @new_map = Game_Map.new
  map = Game_Map.new
  map.setup(map_id)
  @new_map = map
  # Made an accessor method for changing width.
  @new_map.width = 40
  p @new_map.width  #-> 40
  p map.width  #-> 40
  ...

But this line particular could be swapped and the result would be the same.

@new_map = map, @new_map = map.dup, @new_map = map.clone

I solved it but I had to make a copy function. It probably had to do with the map.map being a pointer or something and thus the bane of shallow copy. Thanks though for replying.