Cloning into an object

ruby-talk
1

Thanks for the pointers. I downloaded evil.rb and tried
"become" (used dest.become(source) for the copy) and it did
exactly what I wanted.

I read a little more about become. It looks like it might be
made standard in ruby at some point. Will it have the above
functionality. Or will it do something like what I think the
smalltalk "become" does - change all references to the
destination object to point to the source object. I really
don't want the reference changes because a) it seems very
expensive (search the object space), and b) this would cause
the object id to change.

Anybody know when/if become will be made standard?

···

--- Robert Klemme <bob.news@gmx.net> wrote:

"George Ogata" <g_ogata@optushome.com.au> schrieb im
Newsbeitrag
news:87zmvfx6u9.fsf@optushome.com.au...
> Eric Mahurin <eric_mahurin@yahoo.com> writes:
>
>> Anybody know how to generically copy (shallow like clone)
an
>> object into another object? It would be nice to handle
the
>> case where the objects have a different class, but I would
at
>> least like to know how to do it when the classes are the
same.
>>
>> Here is an example of what I would like to do:
>>
>> dest = Object.new # or String.new if necessary
>> source = "hello world"
>> destid = dest.id
>>
>> source.clone_into(dest)
>>
>> dest -> "hello world"
>> dest.id==destid -> true
>> dest.class -> String
>
> I hear that evil.rb has Object#become, which will do that
with some
> caveats. Search "Object#become" in the list archives for
more info.

If you just want to copy state you can do without evil magic
(although not
working for builtins like String, Array, Fixnum etc.):

class Object
  def set_from(o)
    o.instance_variables.each do |var|
      instance_variable_set( var, o.instance_variable_get(
var ) )
    end
    self
  end
end

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2

Hi --

···

On Sun, 1 May 2005, Eric Mahurin wrote:

I read a little more about become. It looks like it might be
made standard in ruby at some point. Will it have the above
functionality. Or will it do something like what I think the
smalltalk "become" does - change all references to the
destination object to point to the source object. I really
don't want the reference changes because a) it seems very
expensive (search the object space), and b) this would cause
the object id to change.

I thought that was the whole point of "become". Certainly it doesn't
make sense for references to object x to persist in being reference to
object x if object x has "become" object y. (The idea of having this
in Ruby doesn't appeal to me, but that's my understanding of its
premise, anyway.)

David

--
David A. Black
dblack@wobblini.net

3

Hi,

At Sun, 1 May 2005 12:17:03 +0900,
Eric Mahurin wrote in [ruby-talk:140630]:

Anybody know when/if become will be made standard?

When: time_t wrap arounds (where sizeof(time_t) == 8), perhaps.
If: Matz.become(Evil) executed successfully.

···

--
Nobu Nakada