comment on

You can tie in the attribute handler, so you can untie there, too. So, a closure sent as an extra argument to the constructor works:

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

{   package Array::Nonempty::Attr;
    use Attribute::Handlers;

    sub Nonempty :ATTR(ARRAY) {
        my $referer = $_[2];
        tie @$referer, 'Array::Nonempty', sub { untie @$referer }
    }

}


{   package Array::Nonempty;
    use Tie::Array;
    use parent -norequire => 'Tie::StdArray';
    use Carp;

    sub CLEAR {
        my $self = shift;
        $self->[0] = [];
    }

    sub TIEARRAY {
        my ($class, $untie) = @_;
        bless [ [], $untie ], $class
    }

    sub EXTEND {
        my ($self, $size) = @_;
        croak "Cannot be empty" if 0 == @{ $self->[0] } && 0 == $size;
        $self->SUPER::EXTEND($size);

        # Prevent "untie attempted while 1 inner references still exis
+t"
        my $untie = $self->[1];
        undef $self;

        $untie->()
    }

}

use parent -norequire => 'Array::Nonempty::Attr';

my %hash_ok = ( answer => 42 );
my %hash_empty = ();

my @keys_ok :Nonempty = keys %hash_ok;
say tied(@keys_ok) // 'not tied';
say for @keys_ok;

my @keys_empty :Nonempty = keys %hash_empty;
[download]

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]

In reply to Re^4: Declaring with my, assigning, and testing in same line (attributes) by choroba
in thread Declaring with my, assigning, and testing in same line by mordibity

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		`&`
	<		`<`
	>		`>`
	[		`[`
	]		`]`

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.


Keep It Simple, Stupid
	PerlMonks