/ 
Petal-0.89
River stage one • 7 direct dependents • 8 total dependents
/ Petal::Doc::PIs

NAME

Petal::Doc::PIs - Processing Instructions Syntax

SYNOPSIS

This is an article, not a module.

SUMMARY

This syntax is used by Petal as a 'canonical' syntax, i.e. both Inline and TAL syntaxes are turned into processing instructions.

It is quite similar to HTML::Template or the Template Toolkit syntaxes and it is quite easy to turn into Perl code.

NAMESPACE

Petal processing instructions used to be prefixed by petal:. Since processing instructions are not meant to support XML namespaces, this has been removed.

STATEMENTS

Variables

Abstract

<?var name="EXPRESSION"?>

Example

<title><?var name="document/title"?></title>

Why?

Because if you don't have things which are replaced by real values in your template, it's probably a static page, not a template :-)

If / Else constructs

Usual stuff:

<?if name="user/is_birthay"?>
  Happy Birthday, $user/real_name!
<?else?>
  What?! It's not your birthday?
  A very merry unbirthday to you! 
<?end?>

You can use petal:condition instead of petal:if, and indeed you can use modifiers:

<?condition name="false:user/is_birthay"?>
  What?! It's not your birthday?
  A very merry unbirthday to you! 
<?else?>
  Happy Birthday, $user/real_name!
<?end?>

Not much else to say!

Loops

Use either petal:for, petal:foreach, petal:loop or petal:repeat. They're all the same thing, which one you use is a matter of taste. Again no surprise:

<h1>Listing of user logins</h1>
<ul>
  <?repeat name="user system/list_users"?>
    <li><?var name="user/login"?> :
        <?var name="user/real_name"?></li>
  <?end?>
</ul>

Variables are scoped inside loops so you don't risk to erase an existing 'user' variable which would be outside the loop. The template engine also provides the following variables for you inside the loop:

<?repeat name="foo bar"?>
  <?var name="__count__"?>    - iteration number, starting at 1
  <?var name="__is_first__"?> - is it the first iteration
  <?var name="__is_last__"?>  - is it the last iteration
  <?var name="__is_inner__"?> - is it not the first and not the last iteration
  <?var name="__even__ "?>    - is the count even
  <?var name="__odd__"?>      - is the count odd
<?end?>

Again these variables are scoped, you can safely nest loops, ifs etc... as much as you like and everything should be fine. And if it's not, it's a bug :-)

Includes

At the moment this is the only way to do includes with Petal. Limited support for XIncludes is planned for the future.

<?include file="include.xml"?>

And it will include the file 'include.xml', using the current object base_dir attribute. Petal includes occur at RUN TIME. That means that there is NO SUPPORT to prevent infinite includes, which is usually not so much of a deal since they happen at run time...

This should let you build templates which have a recursive behavior which can be useful to apply templates to any tree-shaped structure (i.e. sitemaps, threads, etc).

If you want use XML::Parser to include files, you should make sure that the included files are valid XML themselves... FYI XML::Parser chokes on this:

<p>foo</p> <p>bar</p>

But this works:

<div> <p>foo</p> <p>bar</p> </div>

(having only one top element is part of the XML spec).

AUTHOR

Copyright 2002 - Jean-Michel Hiver <jhiver@mkdoc.com>

This module is free software and is distributed under the same license as Perl itself.