Preparing data for Template

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

I have been following this tutorial for creating dynamic content with Template and trying to apply this to my own needs. But I've hit a problem in preparing the data for the template.

Template file

[% SET menuframe = ' menuselect' %]

[% PROCESS admin_menu.tt %]

[% FOREACH frame IN frames %]
    <hr>
    <p><b>[% frame.name %]</b><br>
    [% frame.colour %]</p>
[% END %]
[download]

This does not generate any output for anything within the [% FOREACH ... %] block

Here is the code that extracts some data from the database and prepares it for passing to the Template display code

#!/usr/bin/perl

use Site::Common;
use Site::HTML;

use strict;

my $site = Site::Common->new;
my $html = Site::HTML->new;
my $dbh  = $site->db;

if ($data{'command'} eq 'frames') {
    my $vars = {
        'frames' => \&list_frames,
    };
    warn "Displaying template";        # This gets called
    $html->display("admin_frames", $vars);
} else {
    $html->display("admin_pictures");
}


sub list_frames {
    warn "Building list of frames";        # This is not called
    my @frames;
    my $query = $dbh->prepare("SELECT idFrame, name, colour FROM Frame
+");
    $query->execute();
    while (my ($id, $name, $colour) = $query->fetchrow_array()) {
        my $frame = {
            'id'        => $id,
            'name'        => $name,
            'colour'    => $colour,
        };
        push @frames, $frame;
    }
    return \@frames;
}
[download]

There are a couple of warn statements in there so I can see something of what the code is doing.

Here is the relevant part of Site::HTML...

package Site::HTML;

use Template;
use Site::Variables;
use strict;

my $template = Template->new(INCLUDE_PATH => $Site::Variables::templat
+e_path);

sub display {
    my $self = shift;
    my $file = shift;
    my %vars = @_;
    $template->process("$file.tt", \%vars);
}

1;
[download]

I'm not sure when list_frames is supposed to get called but I'm guessing at the time the hash reference $vars is generated.

Comment on Preparing data for Template Select or Download Code

Replies are listed 'Best First'.
Re: Preparing data for Template by 1nickt (Canon) on Dec 30, 2020 at 23:50 UTC
Hi, "I'm not sure when list_frames is supposed to get called..." It won't get called unless you call it ;-) `'frames' => \&list_frames,` [download] This creates a reference ... To simply call the sub you just want: `'frames' => list_frames(),` [download] See also: https://www.oreilly.com/library/view/advanced-perl-programming/1565922204/ch04.html Hope this helps! The way forward always starts with a minimal test.	[reply] [d/l] [select]
Re^2: Preparing data for Template by Bod (Parson) on Dec 31, 2020 at 00:21 UTC
It won't get called unless you call it ;-) I was kind of assuming that the Template code calls the subroutine at some point! After all, it gets passed the reference... In the example code, `get_user_projects` doesn't seem to be explicitly called. #!/usr/bin/perl use strict; use warnings; use Template; use CGI; $\| = 1; print "Content-type: text/html\n\n"; my $file = 'userinfo.html'; my $vars = { 'version' => 3.14, 'days' => [ qw( mon tue wed thu fri sat sun ) ], 'worklist' => \&get_user_projects, 'cgi' => CGI->new(), 'me' => { 'id' => 'abw', 'name' => 'Andy Wardley', }, }; sub get_user_projects { my $user = shift; my @projects = ... # do something to retrieve data return \@projects; } my $template = Template->new({ INCLUDE_PATH => '/home/abw/websrc/src:/home/abw/websrc/lib', PRE_PROCESS => 'config', }); $template->process($file, $vars) \|\| die $template->error(); [download]	[reply] [d/l] [select]
Re^3: Preparing data for Template by pryrt (Abbot) on Dec 31, 2020 at 00:51 UTC
In the example code, `get_user_projects` doesn't seem to be explicitly called. Not in the Perl. But in the template, the line `[% FOREACH project IN worklist(me.id) %]` calls `worklist` as a function with the appropriate ID as its argument. I would assume that in your code, if you don't change to `'frames' => list_frames()` (as already suggested), then you would need to call the `frames` as a function rather than treating it as a variable: probably like `[% FOREACH frame IN frames() %]` (untested) (But it seems to me that you shouldn't need to call a function from the template, unless the data will change based on some parameter from the template, like the `me.id` argument in the tutorial example. Since you're not feeding anything back to the function, why not just define `frames` as the arrayref rather than the coderef?)	[reply] [d/l] [select]
Re^4: Preparing data for Template by Bod (Parson) on Dec 31, 2020 at 11:05 UTC
Re^5: Preparing data for Template by hippo (Bishop) on Dec 31, 2020 at 11:47 UTC
Some notes below your chosen depth have not been shown here
Re^5: Preparing data for Template by GrandFather (Saint) on Jan 01, 2021 at 09:14 UTC
Some notes below your chosen depth have not been shown here
Re^2: Preparing data for Template by Bod (Parson) on Dec 31, 2020 at 11:17 UTC
Hope this helps! Yes thank you, it does help a lot. However, it makes me wonder how the code in the example works...I was trying to replicate this arrangement as a learning exercise to understand dynamically preparing data based on the template file.	[reply]


Perl-Sensitive Sunglasses
	PerlMonks