From: Robert Klemme <shortcutter@...>
Date: 2009-10-15T03:30:14+09:00
Subject: Re: deep cloning, how?

On 14.10.2009 19:03, Caleb Clausen wrote:

> The documentation of Object#dup seems to suggest that subclasses
> should not override dup, preferring to override clone instead.

Where do you take that from?  In the docs referenced below I cannot find 
anything like that.  The only indication I can see is that #dup uses 
#initialize_copy and we should probably override that instead of #dup 
itself.

> I'm not
> sure why this should be or why overriding dup would be bad. But
> anyway, I would suggest this:
> 
> def deep_clone
>   copy=clone
>   copy.name=@name.clone
>   copy
> end
> 
> just so you can keep the existing semantics of clone as a shallow copy.
> 
> I'm really not sure why there are 2 methods to create shallow copies
> in ruby and what all the differences are supposed to be. Other than
> not overriding dup(?), the only other difference between them that I
> can discover is that clone copies the metaclass of the object, whereas
> dup reverts the copy's metaclass to being just its class. I've been
> wondering about the difference between the 2 recently; I hope someone
> out there can provide some enlightenment on why there are 2 and what
> the differences are.

There are more differences namely in the area of frozen and tainted state.

http://www.ruby-doc.org/core/classes/Object.html#M000351
http://www.ruby-doc.org/core/classes/Object.html#M000352

Kind regards

robert

-- 
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