Recursively display nested lists with Template Toolkit

[friedo]

Template Toolkit does not allow recursively including template files, but you can use a VIEW to recurse over a data structure. VIEWs are still experimental but it works for me.

use Template;
use strict;
use warnings;

my $t = Template->new;
my @nodes = (
{name => "one"},
{name => "two", children => [ {name => "red"},
                              {name => "green"} ] },
{name => "three", children => [
  {name => "blah", children => [
    {name => "yakko" },
    {name => "wacko" },
    {name => "dot" }
   ]
  }
]
} );


$t->process("rec.tt", { nodes => \@nodes } );

And the template:

[% VIEW nested_list %]
  [% BLOCK list %]
    <ul>
      [% FOREACH i IN item %]
        <li>[% i.name %]</li>
        [% IF i.children %]
          [% view.print(i.children.list) %]
        [% END %]
      [% END %]
    </ul>
  [% END %]
[% END %]

[% nested_list.print(nodes) %]

And that outputs:

• one
• two
• red
• green
• three
• blah
• yakko
• wacko
• dot

[jeffa]

Very nice. If you don't mind, i'd like to add how to do this with HTML::Mason for posterity, contrast/compare, etc.

Calling component (nodes.html)

<%init>
use strict;
use warnings;

my @nodes = (
    {name => "one"},
    {name => "two", children => [
        {name => "red"},
        {name => "green"},
    ] },
    {name => "three", children => [
        {name => "blah", children => [
            {name => "yakko" },
            {name => "wacko" },
            {name => "dot" },
        ] },
    ] },
);

$m->comp( 'nodes.mas', nodes => \@nodes );
</%init>

and nodes.mas

<%args>
@nodes
</%args>

<ul>
% foreach my $i (@nodes) {
    <li><% $i->{name} %></li>
%   if (ref( $i->{children} ) eq 'ARRAY') {
%       $m->comp( 'nodes.mas', nodes => $i->{children} );
%   }
% }
</ul>

I added a check to ref() for safety.

[jasonk]

Template Toolkit does allow templates to recurse, if you tell it to:

 RECURSION
   Flag to permit recursion into templates (default: 0).

[friedo]

Thanks, jasonk. For some reason I missed that in the docs.

[denny]

Just what I was looking for this morning - thanks very much :)

[ferz]

I don't understand where print() method (or MACRO) is defined.