Template::Manual::Syntax - Directive syntax, structure and semantics |
Template::Manual::Syntax - Directive syntax, structure and semantics
By default, template directives are embedded within the character sequences
[%
and %]
.
[% PROCESS header %] <h1>Hello World!</h1> <a href="[% page.next %]"><img src="[% icon.next %].gif"></a> [% PROCESS footer %]
You can change the tag characters using the START_TAG
, END_TAG
and
TAG_STYLE
configuration options. You can also use the TAGS
directive to
define a new tag style for the current template file.
You can also set the INTERPOLATE
option to allow simple variable references
to be embedded directly in templates, prefixed by a $
.
# INTERPOLATE = 0 <td>[% name %]</td> <td>[% email %]</td> # INTERPOLATE = 1 <td>$name</td> <td>$email</td>
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.
[% INCLUDE header title = 'Hello World' bgcol = '#ffffff' %] [%INCLUDE menu align='right'%] Name: [% name %] ([%id%])
The #
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.
[%# this entire directive is ignored no matter how many lines it wraps onto %]
In any other position, it causes the remainder of the current line to be treated as a comment.
[% # this is a comment theta = 20 # so is this rho = 30 # <aol>me too!</aol> %]
You can add -
or +
to the immediate start or end of a directive
tag to control the whitespace chomping options. See the PRE_CHOMP
and
POST_CHOMP
options for further details.
[% BLOCK foo -%] # remove trailing newline This is block foo [%- END %] # remove leading newline
The simplest directives are GET
and SET
which retrieve and update
variable values respectively. The GET
and SET
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:
[% SET foo = 10 %] [% GET foo %]
written as:
[% foo = 10 %] [% foo %]
You can also express simple logical statements as implicit GET
directives:
[% title or template.title or 'Default Title' %] [% mode == 'graphics' ? "Graphics Mode Enabled" : "Text Mode" %]
All other directives should start with a keyword specified in UPPER
CASE (but see the ANYCASE
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 stop
which is
entirely separate from the STOP
directive.
[% stop = 'Clackett Lane Bus Depot' %] The bus will next stop at [% stop %] # variable [% STOP %] # directive
Directives such as FOREACH
, WHILE
, BLOCK
, FILTER
, etc., mark the
start of a block which may contain text or other directives up to the matching
END
directive. Blocks may be nested indefinitely. The IF
, UNLESS
,
ELSIF
and ELSE
directives also define blocks and may be grouped together
in the usual manner.
[% 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 %]
Block directives can also be used in a convenient side-effect notation.
[% INCLUDE userinfo FOREACH user = userlist %] [% INCLUDE debugtxt msg="file: $error.info" IF debugging %] [% "Danger Will Robinson" IF atrisk %]
versus:
[% FOREACH user = userlist %] [% INCLUDE userinfo %] [% END %] [% IF debugging %] [% INCLUDE debugtxt msg="file: $error.info" %] [% END %] [% IF atrisk %] Danger Will Robinson [% END %]
The output of a directive can be captured by simply assigning the directive to a variable.
[% headtext = PROCESS header title="Hello World" %] [% people = PROCESS userinfo FOREACH user = userlist %]
This can be used in conjunction with the BLOCK
directive for defining large
blocks of text or other content.
[% 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 %]
Note one important caveat of using this syntax in conjunction with side-effect notation. The following directive does not behave as might be expected:
[% var = 'value' IF some_condition %] # does not work
In this case, the directive is interpreted as (spacing added for clarity)
[% var = IF some_condition %] value [% END %]
rather than
[% IF some_condition %] [% var = 'value' %] [% END %]
The variable is assigned the output of the IF
block which returns
'value'
if true, but nothing if false. In other words, the following
directive will always cause 'var' to be cleared.
[% var = 'value' IF 0 %]
To achieve the expected behaviour, the directive should be written as:
[% SET var = 'value' IF some_condition %]
Multiple FILTER
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.
[% PROCESS somefile FILTER truncate(100) FILTER html %]
The pipe character, |
, can also be used as an alias for FILTER
.
[% PROCESS somefile | truncate(100) | html %]
Multiple directives can be included within a single tag when delimited
by semi-colons. Note however that the TAGS
directive must always
be specified in a tag by itself.
[% IF title; INCLUDE header; ELSE; INCLUDE other/header title="Some Other Title"; END %]
versus
[% IF title %] [% INCLUDE header %] [% ELSE %] [% INCLUDE other/header title="Some Other Title" %] [% END %]
Template::Manual::Syntax - Directive syntax, structure and semantics |