Help with an IF?

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

Given the following code.

  my $link = "err";

  if ($q->param('title') == "Political Animal")
    {
      my $link = "pa";
    }
  elsif ($q->param('title') == "Newslink")
    {
      my $link = "nl";
    }
  elsif ($q->param('title') == "New Slang")
    {
      my $link = "ns";
    }elsif ($q->param('title') == "Rant With Ryan")
    {
      my $link = "rwr";
    }
  elsif ($q->param('title') == "Planet Venus")
    {
      my $link = "pv";
    }
  elsif ($q->param('title') == "All Day Breakfast")
    {
      my $link = "adb";
    }
  else
    {
      my $link = "err";
    }

# add item (tech. replace)
  LSRfm::Database::Podcasts->create({'title' => $q->param('title'),
                                        'description' => $q->param('de
+scription'
                                        'short_description' => $q->par
+am('descri
                                        'picture' => $q->param('pictur
+e'),
                                        'alt' => $q->param('alt'),
                                        'updated' => Class::Date->now(
+),
                                        'link' => $link
                                });
[download]

and say $q->param('title') is Polictical Animal, why is it not validating as a truth? and thus Im getting $link=err?

Yours

Barry Carlyon

Comment on Help with an IF? Download Code

Replies are listed 'Best First'.
Re: Help with an IF? by Melly (Chaplain) on Apr 05, 2006 at 10:08 UTC
Firstly, "==" is numeric comparison - use "eq" for string comparison. I'm also assuming that title isn't "Polictical Animal", which is never going to match "Political Animal", however you handle the comparison... ;) As an extra, this looks like a messy way to handle this sort of case. Try (untested): `%linkhash = ( 'Political Animal' => 'pa', 'Newslink' => 'nw' ); if(defined $linkhash{$q->param('title')}){ $link = $linkhash{$q->param('title')}; } else{ $link = 'err'; }` [download] Tom Melly, tom@tomandlu.co.uk	[reply] [d/l]
Re: Help with an IF? by bart (Canon) on Apr 05, 2006 at 10:14 UTC
Perl is not PHP, Perl has different comparison operators for strings and for numbers. That is because Perl doesn't really let you distinguish between whether a value is a string or a number. So, is `"0" == "00"`? Perl resolves that ambiguity by explicitely making you treat the scalars as strings, or as numbers. `==` is for numbers, `eq` is for strings. See perlop. Oh, and you have one more major problem: you're declaring your `$link` variables every time inside the code blocks. That limits their scope to that block, so there's no way you can access these variables outside those blocks. What you have, is a bunch of independent variables all called `$link`. What you need is one declaration, at the top. You have that. Just drop the `my` on every other line that refers to `$link`. Like this: `my $link = "err"; if ($q->param('title') eq "Political Animal") { $link = "pa"; } ...` [download]	[reply] [d/l] [select]
Re: Help with an IF? by McDarren (Abbot) on Apr 05, 2006 at 10:13 UTC
why is it not validating as a truth? Because you are using a numerical comparision operator (==) to compare two strings. What you want is "eq" See perldoc perlop Now, if you don't mind me saying so.. that big series of if/elsif's really smells! If it were me, I would refactor that into something like so: `my $title = 'Political Animal'; # Or in your case, $q->param('title') my %links_to = ( "Political Animal" => "pa", "Newslink" => "nl", "New Slang" => "ns", "Rant With Ryan" => "rwr", "Planet Venus" => "pv", "All Day Breakfast" => "adb", ); my $link = $links_to{$title}; print $link;` [download] Cheers, Darren :)	[reply] [d/l]
Re: Help with an IF? by Samy_rio (Vicar) on Apr 05, 2006 at 10:01 UTC
Hi, use `eq` instead of `==` Regards, Velusamy R. eval"print uc\"\\c$_\""for split'','j)@,/6%@0%2,`e@3!-9v2)/@\|6%,53!-9@2~j';	[reply] [d/l] [select]