stas 2003/07/15 04:06:02
Modified: src/docs/1.0/guide porting.pod
Log:
document the issue with persistant hash iterator
Revision Changes Path
1.19 +31 -1 modperl-docs/src/docs/1.0/guide/porting.pod
Index: porting.pod
===================================================================
RCS file: /home/cvs/modperl-docs/src/docs/1.0/guide/porting.pod,v
retrieving revision 1.18
retrieving revision 1.19
diff -u -r1.18 -r1.19
--- porting.pod 7 Mar 2003 04:29:59 -0000 1.18
+++ porting.pod 15 Jul 2003 11:06:02 -0000 1.19
@@ -2250,7 +2250,37 @@
You should be especially careful with L<Perl Special
Variables|general::perl_reference::perl_reference/The_Scope_of_the_Special_Perl_Variables>
which cannot be
-lexically scoped. You have to use local() instead.
+lexically scoped. You have to use C<local()> instead.
+
+Here is an example with Perl hash variables, which store the iteration
+state in the hash variable and that state persists between requests
+unless explicitly reset. Consider the following registry script:
+
+ #file:hash_iteration.pl
+ #----------------------
+ our %hash;
+ %hash = map {$_ => 1 } 'a'..'c' unless %hash;
+
+ print "Content-type: text/plain\n\n";
+
+ for (my ($k, $v) = each %hash) {
+ print "$k $v\n";
+ last;
+ }
+
+That script prints different values on the first 3 invocations and
+prints nothing on the 4th, and then repeats the loop. (when you run
+with httpd -X). There are 3 hash key/value pairs in the global
+variable C<%hash>.
+
+In order to get the iteration state to its initial state at the
+beginning of each request, you need to reset the iterator as explained
+in the manpage for the C<each()> operator. So adding:
+
+ keys %hash;
+
+before using C<%hash> solves the problem for the current example.
+
=head1 Generating correct HTTP Headers
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