Recursive dup

Ruby
1

Hi, it seems that “dup” method is not recursive, so if we do:
obj_b = obj_a.dup
then all the attributes of obj_b will be a exact copy of attributes of
obj_a, and not references.

But if an attribute of obj_a is an object containing objects inside
then those will be referenced and not copied. This is:

class A
attr_accessor :att
end

class Obj
attr_accessor :kk
end

obj = Obj.new
obj.kk = “KAKA1”
a=A.new
a.att=obj

a
=> #<A:0xb7bf6de8 @att=#<Obj:0xb7c0dcf0 @kk=“KAKA1”>>

b=a.dup
=> #<A:0xb7becd97 @att=#<Obj:0xb7c0dcf0 @kk=“KAKA1”>>

b.a.kk=“KAKA2”

a
=> #<A:0xb7bf6de8 @att=#<Obj:0xb7c0dcf0 @kk=“KAKA2”>>

So finally, an attribute of an attribute of “a” is been modified when
modifying “b”.
I know that I should personalize “dup” method for class A, but is not
any other way? Does exist any automatic way of doing it?
I expect some method “dup_recursive” that looks for objects into
attributes recursively and clones them instead of reference.

Is there something as it?

Thanks a lot.

2

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Iñaki Baz C. wrote:

| I know that I should personalize “dup” method for class A, but is not
| any other way? Does exist any automatic way of doing it?
| I expect some method “dup_recursive” that looks for objects into
| attributes recursively and clones them instead of reference.

If your storage of objects can be enumerated, you could use .each,
duplicate the objects you store, and re-store them.

That doesn’t seem terribly efficient, though, so proceed with caution
(but it may get you started in the right direction :).

Phillip G.
Twitter: twitter.com/cynicalryan
Blog: http://justarubyist.blogspot.com

Make sure comments and code agree.
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3

Hi –

On Mon, 5 May 2008, Iñaki Baz C. wrote:

attr_accessor :att

So finally, an attribute of an attribute of “a” is been modified when
modifying “b”.
I know that I should personalize “dup” method for class A, but is not
any other way? Does exist any automatic way of doing it?
I expect some method “dup_recursive” that looks for objects into
attributes recursively and clones them instead of reference.

Is there something as it?

The most common idiom for a deep clone is:

new_obj = Marshal.load(Marshal.dump(old_obj))

David

4

2008/5/5, David A. Black [email protected]:

The most common idiom for a deep clone is:

new_obj = Marshal.load(Marshal.dump(old_obj))

It’s simply GREAT !!!

Thanks a lot !