Adding a hash to a CGI param

bradcathey has asked for the wisdom of the Perl Monks concerning the following question:

Fellow Monasterians,

It seems like I've seen this done before, but I can't make this work now. I start by assigning a simple hash to a param (BTW, using CGI::Application). Later, I want to add another key-value pair to that param, so:

#EARLIER
$self->param( 'sql'   => \%sql );

#LATER
$self->param( 'sql'   => { 'page_id' => 45 } );
[download]

This, of course, clobbers the original param and I end up with just the new pair. I suppose I could grab all the pairs back into a hash and then add to it:

my %sql = %{ $self->param('sql') };
$sql{'page_id'} = 45;
$self->param( 'sql'   => \%sql );
[download]

But this seems a bit verbose. *Is* there a way to do this? What's the concept at work here? Thanks in advance.

—Brad
"The important work of moving the world forward does not wait to be done by perfect men." George Eliot

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Re: Adding a hash to a CGI param by davidrw (Prior) on Jan 03, 2008 at 15:35 UTC
I believe this will work: `#EARLIER $self->param( 'sql' => \%sql ); #LATER $self->param( 'sql' )->{page_id} = 45;` [download] Where the concept is that the value of the 'sql' param is a hash reference, so you just need to retrieve that and work with it as if it you had done something like `my $href= \%sql;` In the line above, it simply deferences the return value of `$self->param( 'sql' )` and sets the page_id key to 45.	[reply] [d/l] [select]
Re^2: Adding a hash to a CGI param by bradcathey (Prior) on Jan 03, 2008 at 15:44 UTC
Yes, that worked and I understand the 'concept'. Thanks. I think it might have been the hash reference that was throwing me. I suppose if I were storing an array in the param, I could `push`. —Brad "The important work of moving the world forward does not wait to be done by perfect men." George Eliot	[reply] [d/l]
Re^3: Adding a hash to a CGI param by Anonymous Monk on Jan 03, 2008 at 17:10 UTC
I suppose if I were storing an array in the param, I could `push` . Assuming that what was returned by `$self->param('foo')` was an array reference and not a hash ref, you could indeed say: `push @{ $self->param('foo') }, $element, $anotherelement, $etc;` [download] And, in general, treat the expression as you would any array ref: `$self->param('foo')->[$n] = 42;` [download]	[reply] [d/l] [select]