Simple newbie question

ruby-talk
1

Hi,
I have a piece of code below in which I;
1.....make a new NumberList object and append two MyNumber objects.
2.....copy the NumberList object and append a further MyNumber object.
However after this both objects are the same.
Any help would be greatly appreciated.
Thanks,
Kieran

···

---------------------------------------------------
class MyNumber
  def initialize(x)
  @x=x
  end
  attr_accessor :x
end
class MyNumberList
  def initialize
  @nums = Array.new
  end
  def append(num)
    @nums.push(num)
    self
  end
  def sum
  sum=0
  @nums.each {|s| sum += s.x }
  return sum
  end
end

zl1=MyNumberList.new; zl1.append(MyNumber.new(10));
zl1.append(MyNumber.new(20))
puts zl1.sum
zl2=zl1; zl2.append(MyNumber.new(40))
puts zl1.sum
puts zl2.sum

--
Posted via http://www.ruby-forum.com/.

2

Hi --

Hi,
I have a piece of code below in which I;
1.....make a new NumberList object and append two MyNumber objects.
2.....copy the NumberList object and append a further MyNumber object.
However after this both objects are the same.

[...]

zl2=zl1

That's why they're the same: by doing this assignment, you're storing
a new reference to the object in zl2. But it's still the same object.

David

···

On Thu, 26 Jan 2006, kieran kirwan wrote:

--
David A. Black
dblack@wobblini.net

"Ruby for Rails", from Manning Publications, coming May 1, 2006!

3

kieran kirwan <kieran.kirwan@dto.ie> writes:

Hi,
I have a piece of code below in which I;
1.....make a new NumberList object and append two MyNumber objects.
2.....copy the NumberList object and append a further MyNumber object.
However after this both objects are the same.
Any help would be greatly appreciated.

See <http://www.rubygarden.org/ruby?Make_A_Deep_Copy_Of_An_Object>

zl2=zl1;

As said, you doesn't copy the contents of zl1 in zl2: you make zl2 and
zl1 reference the same objet. What you want to do is to copy the
*contents* of zl1 into zl2.

···

--
Eric Jacoboni, ne il y a 1441718614 secondes