Re: scope of variable

[kcott]

G'day Priyo,

Welcome to the monastery.

Your code raised a number of issues which I'll address first. My comments assume you've posted all relevant code; however, your problem description suggests otherwise. Of course, I have no way of knowing what you've left out; just bear that in mind as you read the following. (These guidelines will help you post a better question next time: "How do I post a question effectively?".)

• You don't declare "$d". ("use strict;" would have picked this up — see strict)
• You don't assign a value to "$d". ("use warnings;" would have picked this up — see warnings)
• You haven't shown any input: I have no idea what data you're processing.
• You haven't shown your output: "everything works fine" (and similar prose) is not particularly helpful.
• Don't use prototypes unless you really need them and know exactly what you're doing (see perlsub - Prototypes).
• Don't use Indirect Object Syntax (see perlobj - Invoking Class Methods).
• You create a new $parser each time getValue() is called: this is unnecessary.
• You don't capture the return value of $parser->parsefile() (see XML::Parser - METHODS).
• You don't read the arguments passed to your handlers (see XML::Parser - HANDLERS).
• You define your handlers inside the getValue subroutine. I don't know what you were trying to achieve by doing this.

Here's a basic script (along the lines that I think you want) which addresses these issues. Consider this a template for reworking your code.

#!/usr/bin/env perl

use strict;
use warnings;

use XML::Parser;

my $parser = XML::Parser::->new(Handlers => {
    Start   => \&hdl_start,
    End     => \&hdl_end,
    Char    => \&hdl_char,
    Default => \&hdl_def,
    Final   => \&hdl_final,
});

my @xml_files
    = qw{./pm_xml_parser_test_file1.xml ./pm_xml_parser_test_file2.xml
+};

for (@xml_files) {
    _init_handler_vars('filename');
    get_value($_);
}

sub get_value {
    my $file = shift;

    my $returned = $parser->parsefile($file);

    if (defined $returned) {
        print "Wanted content: '$returned'\n";
    }
    else {
        print "Wanted content not found!\n";
    }

    return;
}

# Private scope for handler variables
{
    my ($wanted_element, $in_wanted_element,
        $wanted_content, $found_wanted_content);

    sub _init_handler_vars {
        $wanted_element = shift;
        $in_wanted_element = 0;
        $wanted_content = '';
        $found_wanted_content = 0;

        return;
    }

    sub hdl_start {
        my ($expat, $element, $attr, @vals) = @_;

        if ($element eq $wanted_element) {
            $in_wanted_element = 1;
        }

        return;
    }

    sub hdl_end {
        my ($expat, $element) = @_;

        if ($element eq $wanted_element) {
            $in_wanted_element = 0;
        }

        return;
    }

    sub hdl_char {
        my ($expat, $string) = @_;

        if ($in_wanted_element) {
            if ($string) {
                $found_wanted_content = 1;
                $wanted_content =  $string;
            }
        }

        return;
    }

    sub hdl_def {
        my ($expat, $string) = @_;

        # Default handler actions here

        return;
    }

    sub hdl_final {
        my ($expat) = @_;

        return unless $found_wanted_content;
        return $wanted_content;
    }
}

Most of what I have here should be obvious from the issues I identified (and supporting documentation) above. Note that the variables $wanted_element, $in_wanted_element, $wanted_content and $found_wanted_content are only visible to _init_handler_vars() and the handlers themselves (hdl_*()).

Here's my (minimal) test data:

$ cat ./pm_xml_parser_test_file1.xml
<root_element>
    <filename>pm_xml_parser_test_file1.xml</filename>
</root_element>

$ cat ./pm_xml_parser_test_file2.xml
<root_element>
    <filename>pm_xml_parser_test_file2.xml</filename>
</root_element>

Here's the output:

$ pm_xml_parser_test.pl
Wanted content: 'pm_xml_parser_test_file1.xml'
Wanted content: 'pm_xml_parser_test_file2.xml'