Re: how do I copy an array of objects?

Hi AM,

If I get what you are doing correctly, you want to change this

sub generate {
  my ($self, $OBJS) = @_;
}
[download]

sub generate {
  my ($self, [@$OBJS]) = @_;
}
[download]

where you dereference $OBJS then return a reference to the dereferenced array, therefore returning a deep copy. Here is an example of what I mean.

#!/usr/bin/perl -w

use strict;

my $original =[1,2, 3];

my $shallow_original=$original;
my $deep_original=[@$original];

$original->[1]=42;

print "original: @$original\n";
print "shallow: @$shallow_original\n";
print "deep: @$deep_original\n";
[download]

which, when run, would produce

original: 1 42 3
shallow: 1 42 3
deep: 1 2 3
[download]

cheers

thinker

Edit to add return values.
thinker

Comment on Re: how do I copy an array of objects? Select or Download Code

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Re: Re: how do I copy an array of objects? by thinker (Parson) on Nov 12, 2001 at 21:02 UTC
>># NOTE: >># $OBJS is an array of objects, and array elements can also be arrays of objects I should have read the question better before I answered :-) The code I gave will only dereference down 1 layer. The code below will explain this better, I hope. Anyway, I think what you really want is Clone. I just downloaded it to test this code, and already I see it as an invaluable tool in my Perl toolbox. Here is an example of how my earlier code fails, and how Clone can help you. Good luck thinker #!/usr/bin/perl -w use strict; use Clone qw(clone); my $original =[1,2,[3,4,5]]; my $shallow_original=$original; my $deep_original=[@$original]; #deep, but not deep enough!! my $clone_original=clone($original); # this behaves fine. $original->[1]=42; $original->[2][1]=77; print "original: @$original\n"; print "shallow: @$shallow_original\n"; print "deep: @$deep_original\n"; print "shallow[2][1]: $shallow_original->[2][1]\n"; print "deep[2][1]: $deep_original->[2][1]\n"; print "clone[2][1]: $clone_original->[2][1]\n"; [download] The output of which is `original: 1 42 ARRAY(0x80cf9a4) shallow: 1 42 ARRAY(0x80cf9a4) deep: 1 2 ARRAY(0x80cf9a4) shallow[2][1]: 77 deep[2][1]: 77 clone[2][1]: 4` [download]	[reply] [d/l] [select]

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Re: Re: how do I copy an array of objects?
by thinker (Parson) on Nov 12, 2001 at 21:02 UTC

>># NOTE:
>># $OBJS is an array of objects, and array elements can also be arrays of objects

I should have read the question better before I answered :-)
The code I gave will only dereference down 1 layer.
The code below will explain this better, I hope.
Anyway, I think what you really want is Clone.
I just downloaded it to test this code, and already I see it as an invaluable tool in my Perl toolbox.
Here is an example of how my earlier code fails, and how Clone can help you.

Good luck

thinker

#!/usr/bin/perl -w

use strict;
use Clone qw(clone);

my $original =[1,2,[3,4,5]];

my $shallow_original=$original;
my $deep_original=[@$original]; #deep, but not deep enough!!
my $clone_original=clone($original); # this behaves fine.

$original->[1]=42;
$original->[2][1]=77;

print "original: @$original\n";
print "shallow: @$shallow_original\n";
print "deep: @$deep_original\n";

print "shallow[2][1]: $shallow_original->[2][1]\n";
print "deep[2][1]: $deep_original->[2][1]\n";
print "clone[2][1]: $clone_original->[2][1]\n";
[download]

original: 1 42 ARRAY(0x80cf9a4)
shallow: 1 42 ARRAY(0x80cf9a4)
deep: 1 2 ARRAY(0x80cf9a4)
shallow[2][1]: 77
deep[2][1]: 77
clone[2][1]: 4
[download]

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