| Copying IDL objects [message #12981] |
Wed, 30 September 1998 00:00  |
rivers
Messages: 228
Registered: March 1991
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Senior Member |
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I am trying to figure out how to make a copy of an instance of an IDL object.
a = obj_new('myobj')
b = a
; This does not do what I want, it makes a new reference to the same instance
b = obj_copy(a) ; This is what I want
The only way I can see how to do it is:
pro my_obj::copy, out
out->set_a, self.a
out->set_b, self.b
....
end
This means I have to write a set_X function for each field, and each object
class needs its own version of the ::copy routine. This seems crazy.
I seem to recall a post from a few months ago about some ways of generally
getting/setting properties in IDL objects. Any ideas?
____________________________________________________________
Mark Rivers (773) 702-2279 (office)
Argonne National Laboratory (630) 252-0422 (office)
Building 434A (630) 252-0405 (lab)
9700 South Cass Avenue (630) 252-1713 (beamline)
Argonne, IL 60439 (630) 252-0443 (FAX)
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| Re: Copying IDL objects [message #13048 is a reply to message #12981] |
Fri, 02 October 1998 00:00  |
J.D. Smith
Messages: 214
Registered: August 1996
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Senior Member |
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Mark Rivers wrote:
>
> I am trying to figure out how to make a copy of an instance of an IDL object.
>
> a = obj_new('myobj')
> b = a
> ; This does not do what I want, it makes a new reference to the same instance
>
> b = obj_copy(a) ; This is what I want
>
> The only way I can see how to do it is:
>
> pro my_obj::copy, out
> out->set_a, self.a
> out->set_b, self.b
> ....
> end
>
> This means I have to write a set_X function for each field, and each object
> class needs its own version of the ::copy routine. This seems crazy.
>
> I seem to recall a post from a few months ago about some ways of generally
> getting/setting properties in IDL objects. Any ideas?
>
Here's something really dirty that will do the trick. Use it if
desperate:
function obj_copy, obj
o=obj
file=filepath('obj.sav',/TMP)
save,o,FILENAME=file
restore, FILENAME=file
return,o
end
Does the job though. If you're really doing a lot of this, consider
setting up a small ram disk just for this purpose.
JD
--
J.D. Smith |*| WORK: (607) 255-5842
Cornell University Dept. of Astronomy |*| (607) 255-6263
304 Space Sciences Bldg. |*| FAX: (607) 255-5875
Ithaca, NY 14853 |*|
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| Re: Copying IDL objects [message #13054 is a reply to message #12981] |
Fri, 02 October 1998 00:00 |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Hi Folks,
I wrote just a couple of minutes ago:
> This seems like a lot of work. I think I would write this
> function something like this:
>
> PRO My_Obj::Copy, out
> tags = N_Tags(self)
> For j=0,tags-1 DO out.(j} = self.(j)
> END
Mark Rivers kindly points out to me that this doesn't work,
for the simple reason that self is not a structure (even
though it can be accessed as if it were a structure in
a method). Thus, N_Tags returns a 0.
To make it work, I have to do this (with a bit of error
checking too :-):
PRO My_Obj::Copy, out
selfClass = Obj_Class(self)
outClass = Obj_Class(out)
IF selfClass NE outClass THEN BEGIN
ok = Dialog_Message('Object classes not identical.)
RETURN
END
ok = Execute('struct = {' + selfClass + '}')
tags = N_Tags(struct)
For j=0,tags-1 DO out.(j) = self.(j)
END
Cheers,
David
----------------------------------------------------------
David Fanning, Ph.D.
Fanning Software Consulting
E-Mail: davidf@dfanning.com
Phone: 970-221-0438, Toll-Free Book Orders: 1-888-461-0155
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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| Re: Copying IDL objects [message #13057 is a reply to message #12981] |
Fri, 02 October 1998 00:00 |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Mark Rivers (rivers@cars3.uchicago.edu) writes:
> I am trying to figure out how to make a copy of an instance of an IDL object.
>
> a = obj_new('myobj')
> b = a
> ; This does not do what I want, it makes a new reference to the same instance
>
> b = obj_copy(a) ; This is what I want
I thought Replicate might do it, but I see it also just
replicates the object reference, not the actual object.
> The only way I can see how to do it is:
>
> pro my_obj::copy, out
> out->set_a, self.a
> out->set_b, self.b
> ....
> end
>
> This means I have to write a set_X function for each field, and each object
> class needs its own version of the ::copy routine. This seems crazy.
This seems like a lot of work. I think I would write this
function something like this:
PRO My_Obj::Copy, out
tags = N_Tags(self)
For j=0,tags-1 DO out.(j} = self.(j)
END
The only drawback is that N_Tags (and Tag_Names, too) will
only find the tags or fields in the outermost structure.
I do have a little recursive function on my web page to
find *all* the tags in an embedded structure definition.
http://www.dfanning.com/tips/recursive_struct_tags.html
Cheers,
David
----------------------------------------------------------
David Fanning, Ph.D.
Fanning Software Consulting
E-Mail: davidf@dfanning.com
Phone: 970-221-0438, Toll-Free Book Orders: 1-888-461-0155
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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