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

Hi,

This is actually more of a design question. I'm using XML::XPath to do some simple XML parsing and writing. I have the following subroutine:

sub createPath {
    my $path = shift;
    if ($xp->exists($path)) {
        print "Path already exists, overwrite element (N/Y): ";
        my $response = <STDIN>;
        chomp($response);
        unless (lc($response) eq 'y') {
            print "Path creation call will be ignored\n";
            return 0;
        }
    }
    print "Creating node...";
    $xp->createNode($path) or die "Could not create node: $!";

}

[download]

See the obvious problem (that I missed to begin with, somehow)? The 'print "Creating node...";' statement will never be reached. Can anyone think of an elegant way (that actually works :) to rewrite this without having to widen the scope of $response by moving the unless out of the if block? Or would I be best off just to do that?

Also, about the lines my $response = <STDIN>; chomp($response); I'm sure there's a way to write this in one statement, but I've sadly forgotten. Can anyone remind me?

Thanks :)

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Re: XML::XPath path creation problem
by BrowserUk (Patriarch) on Jan 30, 2003 at 06:09 UTC

    Probably not the way I would code it from scratch, but I can't actually see anything wrong with your original code. A simplistic test shows that it works as you'd expect.

    The print "Creating node..."; will be reached if $path doesn't exist or if $path does exists and the user responds Y to the prompt. 

    package Test::test;

sub new { return bless \rand, shift; }
sub exists{ shift; shift(); }
sub createNode{ return print 'Node created'.$/; }

package main;
my $xp = Test::test->new();

createPath( );
createPath( 'test');

sub createPath {
  my $path = shift;
  if ($xp->exists($path)) {
    print "Path already exists, overwrite element (N/Y): ";
    my $response = <STDIN>;
    chomp( $response );
    unless (lc($response) eq 'y') {
      print "Path creation call will be ignored\n";
      return 0;
    }
 }
  print "Creating node...";
  $xp->createNode($path) or die "Could not create node: $!";
}
__END__
c:\test>junk
Creating node...Node created
Path already exists, overwrite element (N/Y): y
Creating node...Node created

c:\test>

    [download]

    With regard to the chomp question, you could do chomp( my $response = <STDIN> );. Whether this is 'better' is your decision.

    Examine what is said, not who speaks.

    The 7th Rule of perl club is -- pearl clubs are easily damaged. Use a diamond club instead.

[reply]
[d/l]
[select]

      Thanks for the reply

      The orginal code I posted was actually 'correct' (haven't had that happen before :). I just figured out what the problem was. The last print statement didn't have a newline on it, so it was printing, but was getting covered up by my shell prompt so I didn't think it was being reached. This would be a bug right? Would seem rather annoying for a specified behavior.

      This is using perl, v5.8.0 built for i386-linux-thread-multi on Redhat 8.0 with Konsole 1.1.3 using KDE 3.0.3-8.

      Strangest problem I've had in a while. Thanks for the help :)

[reply]
Re: XML::XPath path creation problem
by Anonymous Monk on Jan 30, 2003 at 05:29 UTC

    To clarify what I mean by "having to widen the scope of $response" Something like:

    sub createPath {
    my $path = shift;
    my $response = 'n';
    if ($xp->exists($path)) {
        print "Path already exists, overwrite element (N/Y): ";
        $response = <STDIN>;
        chomp($response);
    }
    print $response, "\n";
    unless (lc($response) eq 'y') {
        print "Path creation call will be ignored\n";
        return 0;
    }
    print "Creating node...";
}

    [download]

    Except even if 'y' is entered it never seems to execute the final print statement. Any guesses?

[reply]
[d/l]

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