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Re: Easy cloning leaving out selected attributes

by jeffa (Bishop)
on Apr 17, 2012 at 00:03 UTC ( #965414=note: print w/replies, xml ) Need Help??


in reply to Easy cloning leaving out selected attributes

But isn't that the point of cloning? If you want an object to have default attributes then just make a new one.


jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

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Re^2: Easy cloning leaving out selected attributes
by mzedeler (Pilgrim) on Apr 17, 2012 at 11:31 UTC

    The point is that some (few) attributes should never be cloned, while others should. In this case, I have some objects that are stored through KioukuDB, and it never makes sense that they get the same id as the original object.

    I have a role that provides default ids, so it would be nice to have the clone method default to that.

    Another thing I need to differentiate is between some attributes that should be shallow clones and others that should be deep clones (using the clone() method on them, of course).

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[Corion]: hippo: If you have a Unicode-wise Perl then likely some zero-width characters in $x would work. Maybe $x = "\x{200b}" works.
[Corion]: Hmm - no, that outputs 1 for me on 5.14 - perl -wle "my $x = qq(\x{200b}); warn $x; warn length $x"
[hippo]: Smart - I'll give that a go. Thanks.
[hippo]: Ah
[Corion]: But maybe there is some other Unicode string that will be true but have a zero width
[hippo]: For explanation, I've seen this construct in someone else's code (no names, no pack drill) and couldn't think of a situation to trigger it.
[Corion]: You'll have to look somewhere esoteric for that. Maybe some tied variable or special dualvar can also trigger that. But it's certainly not a common occurrence
[Corion]: And on 5.20, the following also outputs no find:perl -wle 'for my $x ("\x{2000}".."\ x{1fffff}") { if( $x && ! length $x ) { warn qq(<$x>); warn length $x; die } }'

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