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POEquivalent of "shift" for a hash to create a $class->next() method
 

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    <p>I almost feel like saying "it's me again!".</p> <p>Anyway, here we go.</p> <p>I like using <code>while $object-&gt;next()</code> style constructs. They appeal to me and seem "neat".</p> <p>Now, when the thing I'm iterating over is an array, it's straightforward ("<code>shift @ary or return undef</code>")</p> <pre><code>sub next { my ( $self, $args ) = @_; my $next = shift @{ $self-&gt;{list_of_things} } or return undef; my ( $car, $engine_size, $color ) = split( /\Q$opts-&gt;{fieldsep}/, $next ); $self-&gt;car = $host; $self-&gt;engine_size = $engine_size; $self-&gt;color = $color; </code></pre> <p>}</p> <p>In this example I use AUTOLOAD to create the getters and setters and then have those instance variables available in my object during the <code>while</code> loop.</p> <p>I'd like to do something similar but with the "list_of_things" being a <code>%hash</code>.</p> <p>Here's a non-OO example that doesn't make it into the first iteration. Any ideas why?</p> <p>(The total "list_of_things" is not that big - maybe 100 entries - so to do a <code>keys(%{$hash})</code> every time doesn't seem too wasteful to me).</p> <pre><code>use strict; use warnings; use Data::Dumper; my $list_of_things = { volvo =&gt; { color =&gt; "red", engine_size =&gt; 2000, }, bmw =&gt; { color =&gt; "black", engine_size =&gt; 2500, }, mini =&gt; { color =&gt; "british racing green", engine_size =&gt; 1200, } }; sub next { my $args = $_; my @list = keys( %{$list_of_things} ); return undef if scalar @list == "0"; my $next = $list_of_things-&gt;{ $list[0] }; delete $list_of_things-&gt;{ $list[0] }; return $next; } while ( next()) { print Dumper $_; print scalar keys %{ $list_of_things } } </code></pre> <p>Is there a better way of doing this? Am I doing something crazy?</p> <h1>EDIT:</h1> <p>I tried Ikegami's suggestion. Of course, Ikegami's example works flawlessly. When I try and abstract a little, so that all that is exposed to the object is a next->() method, I get the same "perl-going-to-100%-cpu" problem as in my original example.</p> <p>Here's a non-OO example:</p> <pre><code>use Data::Dumper qw( Dumper ); sub make_list_iter { my @list = @_; return sub { @list ? shift(@list) : () }; } sub next { make_list_iter( keys %$hash ); } my $hash = { ... }; while ( my ($k) = next-&gt;() ) { print Dumper $hash-&gt;{$k}; } </code></pre> <p>It does not seem to get past the first step of the while() loop.</p> <p>I am obviously missing something here...</p>
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    1. COThere's a ton of CPAN modules that will do this for you... [`List::Gen`](http://search.cpan.org/perldoc?List::Gen), [`Array::Iterator`](http://search.cpan.org/perldoc?Array::Iterator), etc. Why reinvent the wheel?
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    2. CO@zaid - Good point... And I agree. There are two reasons: * I am not able to use external modules without them going through an extended process to get blessed by security * I want to understand!
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