in reply to Re^4: language selection via libxml
in thread language selection via libxml

"/language/$language/widget[\@ID=$id]"    - OK

[download]
Well, it is a valid syntax, but the meaning is different: it tries to find a widget whose ID attribute has the same value as the text of the child of widget whose name is $id. Barewords are not promoted to strings in XPath.
لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

Replies are listed 'Best First'.
Re^6: language selection via libxml
by tangent (Parson) on Jan 20, 2014 at 13:21 UTC
    I am trying to get this as I believe Xpath expressions to be very powerful and I've always had a hard time understanding them.

    The two examples marked OK above seem to behave the same way: 

    use XML::LibXML;
my $tree = XML::LibXML->load_xml(string => <<'EOT');
<?xml version="1.0"?>
<language>
    <english>
        <widget ID="1">input</widget>
        <widget ID="2">output</widget>
    </english>
    <deutsch>
        <widget ID="1">eingabe</widget>
        <widget ID="2">ausgabe</widget>
    </deutsch>
</language>
EOT

test('english',1);
test('deutsch',1);

sub test {
    my ($language,$id) = @_;
    my @result=$tree->findnodes("/language/$language/widget[\@ID=$id]"
+);
    print $_->textContent . "\n" for @result;
    my @result2=$tree->findnodes("/language/$language/widget[\@ID='$id
+']");
    print $_->textContent . "\n" for @result2;
}

    [download]
    Output: 
    input
input
eingabe
eingabe

    [download]
[reply]
[d/l]
[select]
      OK, numbers do not have to be enclosed in quotes, and a valid identifier cannot start with a digit. Try using "a" and "b" as the identifiers, though.
      لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
[reply]
        I see. So when I changed the ID values to 'a' and 'b' the only one that worked was the one with single quotes: 
        "/language/$language/widget[\@ID='$id']"

        [download]
        I'm not quite sure what you mean by "a valid identifier cannot start with a digit" - what does 'identifier' refer to?
[reply]
[d/l]

In Section Seekers of Perl Wisdom