NAME
Template::Declare - Perlish declarative templates
SYNOPSIS
"Template::Declare" is a pure-perl declarative HTML/XUL/RDF/XML
templating system.
Yes. Another one. There are many others like it, but this one is ours.
A few key features and buzzwords:
* All templates are 100% pure perl code
* Simple declarative syntax
* No angle brackets
* "Native" XML namespace and declarator support
* Mixins
* Inheritance
* Public and private templates
USAGE
Basic usage
##############################
# Basic HTML usage:
###############################
package MyApp::Templates;
use Template::Declare::Tags; # defaults to 'HTML'
use base 'Template::Declare';
template simple => sub {
html {
head {}
body {
p {'Hello, world wide web!'}
}
}
};
package main;
use Template::Declare;
Template::Declare->init( roots => ['MyApp::Templates']);
print Template::Declare->show( 'simple');
# Output:
#
#
#
#
#
# Hello, world wide web!
#
#
#
###############################
# Let's do XUL!
###############################
package MyApp::Templates;
use base 'Template::Declare';
use Template::Declare::Tags 'XUL';
template main => sub {
xml_decl { 'xml', version => '1.0' };
xml_decl { 'xml-stylesheet', href => "chrome://global/skin/", type => "text/css" };
groupbox {
caption { attr { label => 'Colors' } }
radiogroup {
for my $id ( qw< orange violet yellow > ) {
radio {
attr {
id => $id,
label => ucfirst($id),
$id eq 'violet' ?
(selected => 'true') : ()
}
}
} # for
}
}
};
package main;
Template::Declare->init( roots => ['MyApp::Templates']);
print Template::Declare->show('main')
# Output:
#
#
#
#
#
#
#
#
#
#
#
#
A slightly more advanced example
In this example, we'll show off how to set attributes on HTML tags, how
to call other templates and how to declare a *private* template that
can't be called directly. We'll also show passing arguments to
templates.
package MyApp::Templates;
use Template::Declare::Tags;
use base 'Template::Declare';
private template 'header' => sub {
head {
title { 'This is a webpage'};
meta { attr { generator => "This is not your father's frontpage"}}
}
};
private template 'footer' => sub {
my $self = shift;
my $time = shift || gmtime;
div { attr { id => "footer"};
"Page last generated at $time."
}
};
template simple => sub {
my $self = shift;
my $user = shift || 'world wide web';
html {
show('header');
body {
p { attr { class => 'greeting'};
"Hello, $user!"};
};
show('footer');
}
};
package main;
use Template::Declare;
Template::Declare->init( roots => ['MyApp::Templates']);
print Template::Declare->show( 'simple', 'TD user');
# Output:
#
#
#
# This is a webpage
#
#
#
#
# Hello, TD user!
#
#
#
#
For more options, especially the "native" XML namespace support and more
samples, see Template::Declare::Tags.
Postprocessing
Sometimes you just want simple syntax for inline elements. The following
shows how to use a postprocessor to emphasize text _like this_.
package MyApp::Templates;
use Template::Declare::Tags;
use base 'Template::Declare';
template before => sub {
h1 {
outs "Welcome to ";
em { "my"};
outs " site. It's ";
em { "great"};
outs "!";
};
};
template after => sub {
h1 { "Welcome to _my_ site. It's _great_!"};
h2 { outs_raw "This is _not_ emphasized."};
};
package main;
use Template::Declare;
Template::Declare->init( roots => ['MyApp::Templates'], postprocessor => \&emphasize);
print Template::Declare->show( 'before');
print Template::Declare->show( 'after');
sub emphasize {
my $text = shift;
$text =~ s{_(.+?)_}{$1}g;
return $text;
}
# Output:
#
# Welcome to
# my site. It's
# great!
# Welcome to my site. It's great!
# This is _not_ emphasized.
Multiple template roots (search paths)
Inheritance
Aliasing
METHODS
init
This *class method* initializes the "Template::Declare" system.
roots
postprocessor
show TEMPLATE_NAME
Call "show" with a "template_name" and "Template::Declare" will render
that template. Content generated by show can be accessed with the
"output" method if the output method you've chosen returns content
instead of outputting it directly.
(If called in scalar context, this method will also just return the
content when available).
alias
alias Some::Clever::Mixin under '/mixin';
import_templates
import_templates Wifty::UI::something under '/something';
path_for $template
Returns the path for the template name to be used for show, adjusted
with paths used in import_templates.
has_template PACKAGE TEMPLATE_NAME SHOW_PRIVATE
Takes a package, template name and a boolean. The boolean determines
whether to show private templates.
Returns a reference to the template's code if found. Otherwise, returns
undef.
This method is an alias for "resolve_template"
resolve_template TEMPLATE_PATH INCLUDE_PRIVATE_TEMPLATES
Turns a template path ("TEMPLATE_PATH") into a "CODEREF". If the boolean
"INCLUDE_PRIVATE_TEMPLATES" is true, resolves private template in
addition to public ones.
First it looks through all the valid Template::Declare roots. For each
root, it looks to see if the root has a template called $template_name
directly (or via an "import" statement). Then it looks to see if there
are any "alias"ed paths for the root with prefixes that match the
template we're looking for.
register_template PACKAGE TEMPLATE_NAME CODEREF
This method registers a template called "TEMPLATE_NAME" in package
"PACKAGE". As you might guess, "CODEREF" defines the template's
implementation.
register_template PACKAGE TEMPLATE_NAME CODEREF
This method registers a private template called "TEMPLATE_NAME" in
package "PACKAGE". As you might guess, "CODEREF" defines the template's
implementation.
Private templates can't be called directly from user code but only from
other templates.
PITFALLS
We're reusing the perl interpreter for our templating langauge, but Perl
was not designed specifically for our purpose here. Here are some known
pitfalls while you're scripting your templates with this module.
* It's quite common to see tag sub calling statements without trailing
semi-colons right after "}". For instance,
template foo => {
p {
a { attr { src => '1.png' } }
a { attr { src => '2.png' } }
a { attr { src => '3.png' } }
}
};
is equivalent to
template foo => {
p {
a { attr { src => '1.png' } };
a { attr { src => '2.png' } };
a { attr { src => '3.png' } };
};
};
But "xml_decl" is a notable exception. Please always put a trailing
semicolon after "xml_decl { ... }", or you'll mess up the outputs.
* Another place that requires trailing semicolon is the statements
before a Perl looping statement, an if statement, or a "show" call.
For example:
p { "My links:" };
for (@links) {
with( src => $_ ), a {}
}
The ";" after " p { ... } " is required here, or Perl will complain
about syntax errors.
Another example is
h1 { 'heading' }; # this trailing semicolon is mandatory
show 'tag_tag'
* Literal strings that have tag siblings won't be captured. So the
following template
p { 'hello'; em { 'world' } }
produces
world
instead of the desired output
hello
world
You can use "outs" here to solve this problem:
p { outs 'hello'; em { 'world' } }
Note you can always get rid of the "outs" crap if the string literal
is the only element of the containing block:
p { 'hello, world!' }
BUGS
Crawling all over, baby. Be very, very careful. This code is so cutting
edge, it can only be fashioned from carbon nanotubes. But we're already
using this thing in production :) Make sure you have read the PITFALL
section above :)
Some specific bugs and design flaws that we'd love to see fixed.
Output isn't streamy.
If you run into bugs or misfeatures, please report them to
"bug-template-declare@rt.cpan.org".
SEE ALSO
Template::Declare::Tags, Template::Declare::TagSet,
Template::Declare::TagSet::HTML, Template::Declare::TagSet::XUL, Jifty.
AUTHOR
Jesse Vincent
COPYRIGHT
Copyright 2006-2007 Best Practical Solutions, LLC