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<h1 class="headline">Template::Manual::Syntax</h1>
<h2 class="subhead">Directive syntax, structure and semantics</h1>
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<li class=""><a href="#Tag_Styles">Tag Styles</a></li>
<li class=""><a href="#Comments">Comments</a></li>
<li class=""><a href="#Chomping_Whitespace">Chomping Whitespace</a></li>
<li class=""><a href="#Implicit_Directives_GET_and_SET">Implicit Directives: GET and SET</a></li>
<li class=""><a href="#Block_Directives">Block Directives</a></li>
<li class=""><a href="#Capturing_Block_Output">Capturing Block Output</a></li>
<li class=""><a href="#Chaining_Filters">Chaining Filters</a></li>
<li class=""><a href="#Multiple_Directive_Blocks">Multiple Directive Blocks</a></li>
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<h1 id="Tag_Styles" onclick="switch_section(this)" title="Click title to show/hide section content.">Tag Styles</h1>
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<p>
By default, template directives are embedded within the character
sequences <code>[%</code> and <code>%]</code>.
</p>
<pre>[% PROCESS header %]
<h1>Hello World!</h1>
<a href="[% page.next %]"><img src="[% icon.next %].gif"></a>
[% PROCESS footer %]</pre>
<p>
You can change the tag characters using the <code>START_TAG</code>,
<code>END_TAG</code> and <code>TAG_STYLE</code> configuration options.
You can also use the <code>TAGS</code> directive to define a new tag
style for the current template file.
</p>
<p>
You can also set the <code>INTERPOLATE</code> option to allow simple
variable references to be embedded directly in templates, prefixed by a
<code>$</code>.
</p>
<pre># INTERPOLATE = 0
<td>[% name %]</td>
<td>[% email %]</td>
# INTERPOLATE = 1
<td>$name</td>
<td>$email</td></pre>
<p>
Directives may be embedded anywhere in a line of text and can be split
across several lines. Insignificant whitespace is generally ignored
within the directive.
</p>
<pre>[% INCLUDE header
title = 'Hello World'
bgcol = '#ffffff'
%]
[%INCLUDE menu align='right'%]
Name: [% name %] ([%id%])</pre>
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<h1 id="Comments" onclick="switch_section(this)" title="Click title to show/hide section content.">Comments</h1>
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<p>
The <code>#</code> character is used to indicate comments within a
directive. When placed immediately inside the opening directive tag, it
causes the entire directive to be ignored.
</p>
<pre>[%# this entire directive is ignored no
matter how many lines it wraps onto
%]</pre>
<p>
In any other position, it causes the remainder of the current line to be
treated as a comment.
</p>
<pre>[% # this is a comment
theta = 20 # so is this
rho = 30 # <aol>me too!</aol>
%]</pre>
</div>
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<h1 id="Chomping_Whitespace" onclick="switch_section(this)" title="Click title to show/hide section content.">Chomping Whitespace</h1>
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</div>
<div class="body">
<p>
You can add <code>-</code> or <code>+</code> to the immediate start or
end of a directive tag to control the whitespace chomping options. See
the <code>PRE_CHOMP</code> and <code>POST_CHOMP</code> options for
further details.
</p>
<pre>[% BLOCK foo -%] # remove trailing newline
This is block foo
[%- END %] # remove leading newline</pre>
</div>
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<div class="section">
<div class="head">
<h1 id="Implicit_Directives_GET_and_SET" onclick="switch_section(this)" title="Click title to show/hide section content.">Implicit Directives: GET and SET</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The simplest directives are <code>GET</code> and <code>SET</code> which
retrieve and update variable values respectively. The <code>GET</code>
and <code>SET</code> keywords are actually optional as the parser is
smart enough to see them for what they really are (but note the caveat
below on using side-effect notation). Thus, you'll generally see:
</p>
<pre>[% SET foo = 10 %]
[% GET foo %]</pre>
<p>
written as:
</p>
<pre>[% foo = 10 %]
[% foo %]</pre>
<p>
You can also express simple logical statements as implicit
<code>GET</code> directives:
</p>
<pre>[% title or template.title or 'Default Title' %]
[% mode == 'graphics' ? "Graphics Mode Enabled" : "Text Mode" %]</pre>
<p>
All other directives should start with a keyword specified in UPPER CASE
(but see the <code>ANYCASE</code> option). All directives keywords are in
UPPER CASE to make them visually distinctive and to distinguish them from
variables of the same name but different case. It is perfectly valid, for
example, to define a variable called <code>stop</code> which is entirely
separate from the <code>STOP</code> directive.
</p>
<pre>[% stop = 'Clackett Lane Bus Depot' %]
The bus will next stop at [% stop %] # variable
[% STOP %] # directive</pre>
</div>
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<div class="section">
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<h1 id="Block_Directives" onclick="switch_section(this)" title="Click title to show/hide section content.">Block Directives</h1>
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</div>
<div class="body">
<p>
Directives such as <code>FOREACH</code>, <code>WHILE</code>,
<code>BLOCK</code>, <code>FILTER</code>, etc., mark the start of a block
which may contain text or other directives up to the matching
<code>END</code> directive. Blocks may be nested indefinitely. The
<code>IF</code>, <code>UNLESS</code>, <code>ELSIF</code> and
<code>ELSE</code> directives also define blocks and may be grouped
together in the usual manner.
</p>
<pre>[% FOREACH item = [ 'foo' 'bar' 'baz' ] %]
* Item: [% item %]
[% END %]
[% BLOCK footer %]
Copyright 2000 [% me %]
[% INCLUDE company/logo %]
[% END %]
[% IF foo %]
[% FOREACH thing = foo.things %]
[% thing %]
[% END %]
[% ELSIF bar %]
[% INCLUDE barinfo %]
[% ELSE %]
do nothing...
[% END %]</pre>
<p>
Block directives can also be used in a convenient side-effect notation.
</p>
<pre>[% INCLUDE userinfo FOREACH user = userlist %]
[% INCLUDE debugtxt msg="file: $error.info"
IF debugging %]
[% "Danger Will Robinson" IF atrisk %]</pre>
<p>
versus:
</p>
<pre>[% FOREACH user = userlist %]
[% INCLUDE userinfo %]
[% END %]
[% IF debugging %]
[% INCLUDE debugtxt msg="file: $error.info" %]
[% END %]
[% IF atrisk %]
Danger Will Robinson
[% END %]</pre>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="Capturing_Block_Output" onclick="switch_section(this)" title="Click title to show/hide section content.">Capturing Block Output</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The output of a directive can be captured by simply assigning the
directive to a variable.
</p>
<pre>[% headtext = PROCESS header title="Hello World" %]
[% people = PROCESS userinfo FOREACH user = userlist %]</pre>
<p>
This can be used in conjunction with the <code>BLOCK</code> directive for
defining large blocks of text or other content.
</p>
<pre>[% poem = BLOCK %]
The boy stood on the burning deck,
His fleece was white as snow.
A rolling stone gathers no moss,
And Keith is sure to follow.
[% END %]</pre>
<p>
Note one important caveat of using this syntax in conjunction with
side-effect notation. The following directive does not behave as might be
expected:
</p>
<pre>[% var = 'value' IF some_condition %] # does not work</pre>
<p>
In this case, the directive is interpreted as (spacing added for clarity)
</p>
<pre>[% var = IF some_condition %]
value
[% END %]</pre>
<p>
rather than
</p>
<pre>[% IF some_condition %]
[% var = 'value' %]
[% END %]</pre>
<p>
The variable is assigned the output of the <code>IF</code> block which
returns <code>'value'</code> if true, but nothing if false. In other
words, the following directive will always cause 'var' to be cleared.
</p>
<pre>[% var = 'value' IF 0 %]</pre>
<p>
To achieve the expected behaviour, the directive should be written as:
</p>
<pre>[% SET var = 'value' IF some_condition %]</pre>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="Chaining_Filters" onclick="switch_section(this)" title="Click title to show/hide section content.">Chaining Filters</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Multiple <code>FILTER</code> directives can be chained together in
sequence. They are called in the order defined, piping the output of one
into the input of the next.
</p>
<pre>[% PROCESS somefile FILTER truncate(100) FILTER html %]</pre>
<p>
The pipe character, <code>|</code>, can also be used as an alias for
<code>FILTER</code>.
</p>
<pre>[% PROCESS somefile | truncate(100) | html %]</pre>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="Multiple_Directive_Blocks" onclick="switch_section(this)" title="Click title to show/hide section content.">Multiple Directive Blocks</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Multiple directives can be included within a single tag when delimited by
semi-colons. Note however that the <code>TAGS</code> directive must
always be specified in a tag by itself.
</p>
<pre>[% IF title;
INCLUDE header;
ELSE;
INCLUDE other/header title="Some Other Title";
END
%]</pre>
<p>
versus
</p>
<pre>[% IF title %]
[% INCLUDE header %]
[% ELSE %]
[% INCLUDE other/header title="Some Other Title" %]
[% END %]</pre>
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/manual/Syntax.html last modified 10:57:42 31-May-2007
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