Why isn't my hash empty? 2

[cpjust]

Hi,
I have another problem now.
I have a Perl function that calls a Java function over XMLRPC which returns a Map, but in this test, it should return an empty Map (and does in the Java version of this test); but in Perl Dumper reports it's returning the following:

$VAR1 = {
          '' => undef
        };

The code is:

my %ret = ();
...
%ret = $api->getAllExternalData( $ticketID );

When I use Dumper on %ret right after I declare it, it is empty:

$VAR1 = {};

 

[cpjust]

Another thing I noticed is that when my hash isn't empty (i.e. Java returns a non-empty Map) I get this in Dumper:

$VAR1 = {
          'HASH(0x869ac4)' => undef
        };

Is that a hash inside a hash?

 

[KevinADC]

You can't use a reference as a hash key so that explains the stringification of the reference when used as a hash key. Maybe you should be returning the results to a scalar instead of a hash:

my [red]$[/red]hash_ref = $api->getAllExternalData( $ticketID );
print Dumper \$hash_ref;

------------------------------------------
- Kevin, perl coder unexceptional!

 

[cpjust]

OK, now when I do this in the $api->getAllExternalData() function:

sub getAllExternalData
{
   my $self = shift;
   my $ticketID = shift;
   my $result;
   my $xmlrpc = XML::RPC->new( $url, %{$self->{lwp_useragent}} );
   $result = $xmlrpc->call( $GET_ALL_EXTERNAL_DATA, ($ticketID) );
   print Dumper \$result;
   return $result;
}

I get these results for an empty Java Map & a Map with data:

$VAR1 = \undef;

$VAR1 = \{
            'url_artifacts' => 'External Data for url_artifacts'
          };

Which looks good, but when my test function calls $api->getAllExternalData() and uses Dumper on the hash it returns:

my %ret = $api->getAllExternalData( $ticketID );
print "\n Size of extData = " . keys(%ret) . "\n";
print Dumper \%ret;

I get this from Dumper for an empty & non-Empty Map:

$VAR1 = {
          '' => undef
        };

$VAR1 = {
          'HASH(0x8af480)' => undef
        };

How do I return the hash properly from getAllExternalData() so Dumper reports the same thing both inside & outside the function?

P.S. I'm not a Perl programmer, so I'm not sure what a hash reference is...

 

[KevinADC]

Like this:

my $ret = $api->getAllExternalData( $ticketID );
print Dumper \$ret;
sub getAllExternalData
{
   my $self = shift;
   my $ticketID = shift;
   my $result;
   my $xmlrpc = XML::RPC->new( $url, %{$self->{lwp_useragent}} );
   $result = $xmlrpc->call( $GET_ALL_EXTERNAL_DATA, ($ticketID) );
   print Dumper \$result;
   return $result;
}

------------------------------------------
- Kevin, perl coder unexceptional!

 

[cpjust]

I don't see any difference between that and what I posted?

Anyways, I did some reading about references and got it working by doing this:

sub getAllExternalData
{
	my $self = shift;
	my $ticketID = shift;
	my $result;
	my %extData = ();

	my $xmlrpc = XML::RPC->new( $url, %{$self->{lwp_useragent}} );
	$result = $xmlrpc->call( $GET_ALL_EXTERNAL_DATA, ($ticketID) );

	[b]if ( defined( $result ) ) {
		%extData = %{$result};
	}

	return %extData;[/b]
}

 

[KevinADC]

You did this:

my [red]%[/red]ret = $api->getAllExternalData( $ticketID );

I did this:

my [red]$[/red]ret = $api->getAllExternalData( $ticketID );

Your function was returning a reference to a hash, and a reference is always a scalar. Now you are dereferencing the reference and then returning it as a regular hash. Thats fine as long as you are assigning it to a hash when its returned back from the function. What best is that you understand the difference between what you were doing, what you are now doing, and what I was showing you. I think you do now.

------------------------------------------
- Kevin, perl coder unexceptional!

 

[ishnid]

Good spot Kev.

 

[cpjust]

Ah, now I see, you changed the line that calls the function, not the function itself.
I actually fixed another problem using the same code change, but using a reference to an array instead of hash:

	if ( defined( $result ) ) {
		@keys = @{$result};
	}

Thanks for pointing me in the right direction.