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Unable to display data from hash array

by bar10der (Beadle)
on Jun 14, 2004 at 13:47 UTC ( #366541=perlquestion: print w/replies, xml ) Need Help??

bar10der has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks,
I want to display contents of my oracle table for users to edit it. There are more than 60 fields in the table. I have a saperate table which hold the column names. This is what I am doing-
#Select fieldnames from accfields table in @fields. my @fields = getMultiRows($sql,1,$dbh); ##A saperate perl routine to e +xtract data. my $fields = join(",",@fields); $sql = "SELECT $fields FROM tran WHERE account=?"; my $sth = $dbh->prepare($sql); if(!$sth){$err= "Error preparing query " . $sql . " : ". $dbh->errstr; +} if(!$sth->execute(177)){$err = "Error Executing query " . $sql . " : " +. $dbh->errstr;} my %rows = $sth->fetchrow_hashref; # Now i get the html template and want to populate html form fields wi +th data extracted. All form field names are same as table column na +me. foreach(@fields){ $template->param($_=>$rows{$_}); } return $template->output;
The form is displayed but fields do not show data extracted from database! Where am I making mistake? The html tag in form is -
<input type="text" name="fname" size="40" maxlength="60" value="<!-- T +MPL_VAR fname -->"><!-- TMPL_VAR err_fname -->

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Re: Unable to display data from hash array
by Happy-the-monk (Canon) on Jun 14, 2004 at 13:56 UTC

    Where am I making mistake?

    In a number of ways:
    You are not handling the possible error you store in   $err.
    Consult the DBI.pm documentation how to work with   fetchrow_hashref.
    You did not tell us much about the templating system to understand if there's anything wrong there.

    Cheers, Sören

      Thanks Sören
      I'll give it a go. By the way, there is no problem with the template. I have tested it with some localy defined vars.
Re: Unable to display data from hash array
by benrwebb (Scribe) on Jun 14, 2004 at 16:12 UTC
    I would look at two things:
    First, if you are using HTML:Template, your TMPL_VAR tags don't look right... they should have a "name" as well:
    <TMPL_VAR name="fname">
    Second, it looks like you are doing your assignments the hard way. If you return an AoH (Array of Hashes) from your call to DBI, you can assign that entire array to a loop within your template. For instance:

    my $p = Page->new(); # now we get the info from the database and pass it to the template # in this case, the template needs a reference to an array of hashes # in order to handle the TMPL_LOOP properly. Which is exactly what # dbselect returns. hard to believe :-) $newst->param(news => $p->dbselect($sql,1)); sub dbselect{ my Page $self = shift; my $sql = shift if @_; my $hash = shift if @_; my $db = $self->db(); my $h = $db->prepare($sql) or $self->errorpage("DB problem in sele +ct prepare: " . $db->errstr()); $h->execute() or $self->errorpage("DB problem in select execute: " + . $db->errstr()); my $arrayref; if ($hash){ $arrayref = $h->fetchall_arrayref({}); } else { $arrayref = $h->fetchall_arrayref(); } return $arrayref; }
    I'll break down what just happened there. I'm using an object called Page (I use it for web pages in general), it has a method called dbselect that will query the database for me (the connection is set up elsewhere). $newst is an HTML::Template that I have genereated, so I call the param method of $newst with the output from dbselect assigned to the TMPL_LOOP news. It then fills in my news page with rows of news. Some day I'll update it to limit the number of stories, but I'm basically boring so I don't have that much news to display :-)
    Note the call to fetchall_arrayref({}) within dbselect. Read up on the documentation for DBI, in this format it returns AoH.

    The template that uses this looks like this:
    <table border=0 width='98%' cellspacing=3 cellpadding=3> <TMPL_LOOP NAME="news"> <tr><td> <table width='100%' border=1 cellspacing=1 cellpadding=0> <tr> <th align='left'><TMPL_VAR NAME='summary'></th> <th align='right'><TMPL_VAR NAME='pubdate'></th> </tr> <tr> <td align='left' colspan=255><i>By: <TMPL_VAR NAME +='realname'></i></td> </tr> <tr> <td align='left' colspan=255><TMPL_VAR NAME='conte +nt'></td> </tr> </table> </td></tr> </TMPL_LOOP> </table>
    So you see, by using the AoH with a TMPL_LOOP, I was able to loop through everything with almost no code. Very easy once you understand it.

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