NAME
HTML::Template - Perl module to use HTML Templates from CGI scripts
SYNOPSIS
First you make a template - this is just a normal HTML file with a few
extra tags, the simplest being
For example, test.tmpl:
Test Template
My Home Directory is
My Path is set to
Now create a small CGI program:
#!/usr/bin/perl -w
use HTML::Template;
# open the html template
my $template = HTML::Template->new(filename => 'test.tmpl');
# fill in some parameters
$template->param(HOME => $ENV{HOME});
$template->param(PATH => $ENV{PATH});
# send the obligatory Content-Type and print the template output
print "Content-Type: text/html\n\n", $template->output;
If all is well in the universe this should show something like this in
your browser when visiting the CGI:
My Home Directory is /home/some/directory
My Path is set to /bin;/usr/bin
DESCRIPTION
This module attempts to make using HTML templates simple and natural. It
extends standard HTML with a few new HTML-esque tags - ,
, , , and .
The file written with HTML and these new tags is called a template. It
is usually saved separate from your script - possibly even created by
someone else! Using this module you fill in the values for the
variables, loops and branches declared in the template. This allows you
to separate design - the HTML - from the data, which you generate in the
Perl script.
This module is licensed under the GPL. See the LICENSE section below for
more details.
TUTORIAL
If you're new to HTML::Template, I suggest you start with the
introductory article available on the HTML::Template website:
http://html-template.sourceforge.net
MOTIVATION
It is true that there are a number of packages out there to do HTML
templates. On the one hand you have things like HTML::Embperl which
allows you freely mix Perl with HTML. On the other hand lie home-grown
variable substitution solutions. Hopefully the module can find a place
between the two.
One advantage of this module over a full HTML::Embperl-esque solution is
that it enforces an important divide - design and programming. By
limiting the programmer to just using simple variables and loops in the
HTML, the template remains accessible to designers and other non-perl
people. The use of HTML-esque syntax goes further to make the format
understandable to others. In the future this similarity could be used to
extend existing HTML editors/analyzers to support HTML::Template.
An advantage of this module over home-grown tag-replacement schemes is
the support for loops. In my work I am often called on to produce tables
of data in html. Producing them using simplistic HTML templates results
in CGIs containing lots of HTML since the HTML itself cannot represent
loops. The introduction of loop statements in the HTML simplifies this
situation considerably. The designer can layout a single row and the
programmer can fill it in as many times as necessary - all they must
agree on is the parameter names.
For all that, I think the best thing about this module is that it does
just one thing and it does it quickly and carefully. It doesn't try to
replace Perl and HTML, it just augments them to interact a little
better. And it's pretty fast.
THE TAGS
TMPL_VAR
The tag is very simple. For each tag in the
template you call $template->param(PARAMETER_NAME => "VALUE"). When the
template is output the is replaced with the VALUE text you
specified. If you don't set a parameter it just gets skipped in the
output.
Optionally you can use the "ESCAPE=HTML" option in the tag to indicate
that you want the value to be HTML-escaped before being returned from
output (the old ESCAPE=1 syntax is still supported). This means that the
", <, >, and & characters get translated into ", <, > and
& respectively. This is useful when you want to use a TMPL_VAR in a
context where those characters would cause trouble. Example:
">
If you called param() with a value like sam"my you'll get in trouble
with HTML's idea of a double-quote. On the other hand, if you use
ESCAPE=HTML, like this:
">
You'll get what you wanted no matter what value happens to be passed in
for param. You can also write ESCAPE="HTML", ESCAPE='HTML' and
ESCAPE='1'. Substitute a 0 for the HTML and you turn off escaping, which
is the default anyway.
There is also the "ESCAPE=URL" option which may be used for VARs that
populate a URL. It will do URL escaping, like replacing ' ' with '+' and
'/' with '%2F'.
TMPL_LOOP
...
The tag is a bit more complicated than . The
tag allows you to delimit a section of text and give it a
name. Inside this named loop you place s. Now you pass to
param() a list (an array ref) of parameter assignments (hash refs) for
this loop. The loop iterates over the list and produces output from the
text block for each pass. Unset parameters are skipped. Here's an
example:
In the template:
Name:
Job:
In the script:
$template->param(EMPLOYEE_INFO => [
{ name => 'Sam', job => 'programmer' },
{ name => 'Steve', job => 'soda jerk' },
]
);
print $template->output();
The output in a browser:
Name: Sam
Job: programmer
Name: Steve
Job: soda jerk
As you can see above the takes a list of variable
assignments and then iterates over the loop body producing output.
Often you'll want to generate a 's contents programmatically.
Here's an example of how this can be done (many other ways are
possible!):
# a couple of arrays of data to put in a loop:
my @words = qw(I Am Cool);
my @numbers = qw(1 2 3);
my @loop_data = (); # initialize an array to hold your loop
while (@words and @numbers) {
my %row_data; # get a fresh hash for the row data
# fill in this row
$row_data{WORD} = shift @words;
$row_data{NUMBER} = shift @numbers;
# the crucial step - push a reference to this row into the loop!
push(@loop_data, \%row_data);
}
# finally, assign the loop data to the loop param, again with a
# reference:
$template->param(THIS_LOOP => \@loop_data);
The above example would work with a template like:
Word:
Number:
It would produce output like:
Word: I
Number: 1
Word: Am
Number: 2
Word: Cool
Number: 3
s within s are fine and work as you would expect.
If the syntax for the param() call has you stumped, here's an example of
a param call with one nested loop:
$template->param(LOOP => [
{ name => 'Bobby',
nicknames => [
{ name => 'the big bad wolf' },
{ name => 'He-Man' },
],
},
],
);
Basically, each gets an array reference. Inside the array
are any number of hash references. These hashes contain the name=>value
pairs for a single pass over the loop template.
Inside a , the only variables that are usable are the ones
from the . The variables in the outer blocks are not visible
within a template loop. For the computer-science geeks among you, a
introduces a new scope much like a perl subroutine call. If
you want your variables to be global you can use 'global_vars' option to
new() described below.
TMPL_INCLUDE
This tag includes a template directly into the current template at the
point where the tag is found. The included template contents are used
exactly as if its contents were physically included in the master
template.
The file specified can be an absolute path (beginning with a '/' under
Unix, for example). If it isn't absolute, the path to the enclosing file
is tried first. After that the path in the environment variable
HTML_TEMPLATE_ROOT is tried, if it exists. Next, the "path" option is
consulted. As a final attempt, the filename is passed to open()
directly. See below for more information on HTML_TEMPLATE_ROOT and the
"path" option to new().
As a protection against infinitly recursive includes, an arbitary limit
of 10 levels deep is imposed. You can alter this limit with the
"max_includes" option. See the entry for the "max_includes" option below
for more details.
TMPL_IF
...
The tag allows you to include or not include a block of the
template based on the value of a given parameter name. If the parameter
is given a value that is true for Perl - like '1' - then the block is
included in the output. If it is not defined, or given a false value -
like '0' - then it is skipped. The parameters are specified the same way
as with TMPL_VAR.
Example Template:
Some text that only gets displayed if BOOL is true!
Now if you call $template->param(BOOL => 1) then the above block will be
included by output.
blocks can include any valid HTML::Template
construct - VARs and LOOPs and other IF/ELSE blocks. Note, however, that
intersecting a and a is invalid.
Not going to work:
If the name of a TMPL_LOOP is used in a TMPL_IF, the IF block will
output if the loop has at least one row. Example:
This will output if the loop is not empty.
....
WARNING: Much of the benefit of HTML::Template is in decoupling your
Perl and HTML. If you introduce numerous cases where you have TMPL_IFs
and matching Perl if()s, you will create a maintenance problem in
keeping the two synchronized. I suggest you adopt the practice of only
using TMPL_IF if you can do so without requiring a matching if() in your
Perl code.
TMPL_ELSE
... ...
You can include an alternate block in your TMPL_IF block by using
TMPL_ELSE. NOTE: You still end the block with , not
!
Example:
Some text that is included only if BOOL is true
Some text that is included only if BOOL is false
TMPL_UNLESS
...
This tag is the opposite of . The block is output if the
CONTROL_PARAMETER is set false or not defined. You can use
with just as you can with .
Example:
Some text that is output only if BOOL is FALSE.
Some text that is output only if BOOL is TRUE.
If the name of a TMPL_LOOP is used in a TMPL_UNLESS, the UNLESS block
output if the loop has zero rows.
This will output if the loop is empty.
....
NOTES
HTML::Template's tags are meant to mimic normal HTML tags. However, they
are allowed to "break the rules". Something like:
is not really valid HTML, but it is a perfectly valid use and will work
as planned.
The "NAME=" in the tag is optional, although for extensibility's sake I
recommend using it. Example - "" is acceptable.
If you're a fanatic about valid HTML and would like your templates to
conform to valid HTML syntax, you may optionally type template tags in
the form of HTML comments. This may be of use to HTML authors who would
like to validate their templates' HTML syntax prior to HTML::Template
processing, or who use DTD-savvy editing tools.
In order to realize a dramatic savings in bandwidth, the standard
(non-comment) tags will be used throughout this documentation.
METHODS
new()
Call new() to create a new Template object:
my $template = HTML::Template->new( filename => 'file.tmpl',
option => 'value'
);
You must call new() with at least one name => value pair specifying how
to access the template text. You can use "filename => 'file.tmpl'" to
specify a filename to be opened as the template. Alternately you can
use:
my $t = HTML::Template->new( scalarref => $ref_to_template_text,
option => 'value'
);
and
my $t = HTML::Template->new( arrayref => $ref_to_array_of_lines ,
option => 'value'
);
These initialize the template from in-memory resources. In almost every
case you'll want to use the filename parameter. If you're worried about
all the disk access from reading a template file just use mod_perl and
the cache option detailed below.
You can also read the template from an already opened filehandle, either
traditionally as a glob or as a FileHandle:
my $t = HTML::Template->new( filehandle => *FH, option => 'value');
The four new() calling methods can also be accessed as below, if you
prefer.
my $t = HTML::Template->new_file('file.tmpl', option => 'value');
my $t = HTML::Template->new_scalar_ref($ref_to_template_text,
option => 'value');
my $t = HTML::Template->new_array_ref($ref_to_array_of_lines,
option => 'value');
my $t = HTML::Template->new_filehandle($fh,
option => 'value');
And as a final option, for those that might prefer it, you can call new
as:
my $t = HTML::Template->new(type => 'filename',
source => 'file.tmpl');
Which works for all three of the source types.
If the environment variable HTML_TEMPLATE_ROOT is set and your filename
doesn't begin with /, then the path will be relative to the value of
$HTML_TEMPLATE_ROOT. Example - if the environment variable
HTML_TEMPLATE_ROOT is set to "/home/sam" and I call
HTML::Template->new() with filename set to "sam.tmpl", the
HTML::Template will try to open "/home/sam/sam.tmpl" to access the
template file. You can also affect the search path for files with the
"path" option to new() - see below for more information.
You can modify the Template object's behavior with new. These options
are available:
Error Detection Options
* die_on_bad_params - if set to 0 the module will let you call
$template->param(param_name => 'value') even if 'param_name'
doesn't exist in the template body. Defaults to 1.
* strict - if set to 0 the module will allow things that look like
they might be TMPL_* tags to get by without dieing. Example:
Would normally cause an error, but if you call new with strict
=> 0, HTML::Template will ignore it. Defaults to 1.
* vanguard_compatibility_mode - if set to 1 the module will expect
to see s that look like %NAME% in addition to the
standard syntax. Also sets die_on_bad_params => 0. If you're not
at Vanguard Media trying to use an old format template don't
worry about this one. Defaults to 0.
Caching Options
* cache - if set to 1 the module will cache in memory the parsed
templates based on the filename parameter and modification date
of the file. This only applies to templates opened with the
filename parameter specified, not scalarref or arrayref
templates. Caching also looks at the modification times of any
files included using tags, but again, only if the
template is opened with filename parameter.
This is mainly of use in a persistent environment like
Apache/mod_perl. It has absolutely no benefit in a normal CGI
environment since the script is unloaded from memory after every
request. For a cache that does work for normal CGIs see the
'shared_cache' option below.
Note that different new() parameter settings do not cause a
cache refresh, only a change in the modification time of the
template will trigger a cache refresh. For most usages this is
fine. My simplistic testing shows that using cache yields a 90%
performance increase under mod_perl. Cache defaults to 0.
* shared_cache - if set to 1 the module will store its cache in
shared memory using the IPC::SharedCache module (available from
CPAN). The effect of this will be to maintain a single shared
copy of each parsed template for all instances of HTML::Template
to use. This can be a significant reduction in memory usage in a
multiple server environment. As an example, on one of our
systems we use 4MB of template cache and maintain 25 httpd
processes - shared_cache results in saving almost 100MB! Of
course, some reduction in speed versus normal caching is to be
expected. Another difference between normal caching and
shared_cache is that shared_cache will work in a CGI environment
- normal caching is only useful in a persistent environment like
Apache/mod_perl.
By default HTML::Template uses the IPC key 'TMPL' as a shared
root segment (0x4c504d54 in hex), but this can be changed by
setting the 'ipc_key' new() parameter to another 4-character or
integer key. Other options can be used to affect the shared
memory cache correspond to IPC::SharedCache options - ipc_mode,
ipc_segment_size and ipc_max_size. See IPC::SharedCache for a
description of how these work - in most cases you shouldn't need
to change them from the defaults.
For more information about the shared memory cache system used
by HTML::Template see IPC::SharedCache.
* double_cache - if set to 1 the module will use a combination of
shared_cache and normal cache mode for the best possible
caching. Of course, it also uses the most memory of all the
cache modes. All the same ipc_* options that work with
shared_cache apply to double_cache as well. By default
double_cache is off.
* blind_cache - if set to 1 the module behaves exactly as with
normal caching but does not check to see if the file has changed
on each request. This option should be used with caution, but
could be of use on high-load servers. My tests show blind_cache
performing only 1 to 2 percent faster than cache under mod_perl.
NOTE: Combining this option with shared_cache can result in
stale templates stuck permanently in shared memory!
* file_cache - if set to 1 the module will store its cache in a
file using the Storable module. It uses no additional memory,
and my simplistic testing shows that it yields a 50% performance
advantage. Like shared_cache, it will work in a CGI environment.
Default is 0.
If you set this option you must set the "file_cache_dir" option.
See below for details.
NOTE: Storable using flock() to ensure safe access to cache
files. Using file_cache on a system or filesystem (NFS) without
flock() support is dangerous.
* file_cache_dir - sets the directory where the module will store
the cache files if file_cache is enabled. Your script will need
write permissions to this directory. You'll also need to make
sure the sufficient space is available to store the cache files.
* file_cache_dir_mode - sets the file mode for newly created
file_cache directories and subdirectories. Defaults to 0700 for
security but this may be inconvenient if you do not have access
to the account running the webserver.
* double_file_cache - if set to 1 the module will use a
combination of file_cache and normal cache mode for the best
possible caching. The file_cache_* options that work with
file_cache apply to double_file_cache as well. By default
double_file_cache is 0.
Filesystem Options
* path - you can set this variable with a list of paths to search
for files specified with the "filename" option to new() and for
files included with the tag. This list is only
consulted when the filename is relative. The HTML_TEMPLATE_ROOT
environment variable is always tried first if it exists. In the
case of a file, the path to the including file is
also tried before path is consulted.
Example:
my $template = HTML::Template->new( filename => 'file.tmpl',
path => [ '/path/to/templates',
'/alternate/path'
]
);
NOTE: the paths in the path list must be expressed as UNIX
paths, separated by the forward-slash character ('/').
* search_path_on_include - if set to a true value the module will
search from the top of the array of paths specified by the path
option on every and use the first matching
template found. The normal behavior is to look only in the
current directory for a template to include. Defaults to 0.
Debugging Options
* debug - if set to 1 the module will write random debugging
information to STDERR. Defaults to 0.
* stack_debug - if set to 1 the module will use Data::Dumper to
print out the contents of the parse_stack to STDERR. Defaults to
0.
* cache_debug - if set to 1 the module will send information on
cache loads, hits and misses to STDERR. Defaults to 0.
* shared_cache_debug - if set to 1 the module will turn on the
debug option in IPC::SharedCache - see IPC::SharedCache for
details. Defaults to 0.
* memory_debug - if set to 1 the module will send information on
cache memory usage to STDERR. Requires the GTop module. Defaults
to 0.
Miscellaneous Options
* associate - this option allows you to inherit the parameter
values from other objects. The only requirement for the other
object is that it have a param() method that works like
HTML::Template's param(). A good candidate would be a CGI.pm
query object. Example:
my $query = new CGI;
my $template = HTML::Template->new(filename => 'template.tmpl',
associate => $query);
Now, $template->output() will act as though
$template->param('FormField', $cgi->param('FormField'));
had been specified for each key/value pair that would be
provided by the $cgi->param() method. Parameters you set
directly take precedence over associated parameters.
You can specify multiple objects to associate by passing an
anonymous array to the associate option. They are searched for
parameters in the order they appear:
my $template = HTML::Template->new(filename => 'template.tmpl',
associate => [$query, $other_obj]);
The old associateCGI() call is still supported, but should be
considered obsolete.
NOTE: The parameter names are matched in a case-insensitve
manner. If you have two parameters in a CGI object like 'NAME'
and 'Name' one will be chosen randomly by associate. This
behavior can be changed by the following option.
* case_sensitive - setting this option to true causes
HTML::Template to treat template variable names
case-sensitively. The following example would only set one
parameter without the "case_sensitive" option:
my $template = HTML::Template->new(filename => 'template.tmpl',
case_sensitive => 1);
$template->param(
FieldA => 'foo',
fIELDa => 'bar',
);
This option defaults to off.
* loop_context_vars - when this parameter is set to true (it is
false by default) four loop context variables are made available
inside a loop: __FIRST__, __LAST__, __INNER__, __ODD__. They can
be used with , and to control
how a loop is output. Example:
This only outputs on the first pass.
This outputs every other pass, on the odd passes.
This outputs every other pass, on the even passes.
This outputs on passes that are neither first nor last.
This only outputs on the last pass.
One use of this feature is to provide a "separator" similar in
effect to the perl function join(). Example:
and , .
Would output (in a browser) something like:
Apples, Oranges, Brains, Toes, and Kiwi.
Given an appropriate param() call, of course. NOTE: A loop with
only a single pass will get both __FIRST__ and __LAST__ set to
true, but not __INNER__.
* no_includes - set this option to 1 to disallow the
tag in the template file. This can be used to
make opening untrusted templates slightly less dangerous.
Defaults to 0.
* max_includes - set this variable to determine the maximum depth
that includes can reach. Set to 10 by default. Including files
to a depth greater than this value causes an error message to be
displayed. Set to 0 to disable this protection.
* global_vars - normally variables declared outside a loop are not
available inside a loop. This option makes s like
global variables in Perl - they have unlimited scope. This
option also affects and .
Example:
This is a normal variable: .
Here it is inside the loop:
Normally this wouldn't work as expected, since 's value outside the loop is not available inside the
loop.
The global_vars option also allows you to access the values of
an enclosing loop within an inner loop. For example, in this
loop the inner loop will have access to the value of OUTER_VAR
in the correct iteration:
OUTER:
INNER:
INSIDE OUT:
* filter - this option allows you to specify a filter for your
template files. A filter is a subroutine that will be called
after HTML::Template reads your template file but before it
starts parsing template tags.
In the most simple usage, you simply assign a code reference to
the filter parameter. This subroutine will recieve a single
arguement - a reference to a string containing the template file
text. Here is an example that accepts templates with tags that
look like "!!!ZAP_VAR FOO!!!" and transforms them into
HTML::Template tags:
my $filter = sub {
my $text_ref = shift;
$$text_ref =~ s/!!!ZAP_(.*?)!!!//g;
};
# open zap.tmpl using the above filter
my $template = HTML::Template->new(filename => 'zap.tmpl',
filter => $filter);
More complicated usages are possible. You can request that your
filter receieve the template text as an array of lines rather
than as a single scalar. To do that you need to specify your
filter using a hash-ref. In this form you specify the filter
using the "sub" key and the desired argument format using the
"format" key. The available formats are "scalar" and "array".
Using the "array" format will incur a performance penalty but
may be more convenient in some situations.
my $template = HTML::Template->new(filename => 'zap.tmpl',
filter => { sub => $filter,
format => 'array' });
You may also have multiple filters. This allows simple filters
to be combined for more elaborate functionality. To do this you
specify an array of filters. The filters are applied in the
order they are specified.
my $template = HTML::Template->new(filename => 'zap.tmpl',
filter => [
{ sub => \&decompress,
format => 'scalar' },
{ sub => \&remove_spaces,
format => 'array' }
]);
The specified filters will be called for any TMPL_INCLUDEed
files just as they are for the main template file.
param()
param() can be called in a number of ways
1) To return a list of parameters in the template :
my @parameter_names = $self->param();
2) To return the value set to a param :
my $value = $self->param('PARAM');
3) To set the value of a parameter :
# For simple TMPL_VARs:
$self->param(PARAM => 'value');
# with a subroutine reference that gets called to get the value
# of the scalar. The sub will recieve the template object as a
# parameter.
$self->param(PARAM => sub { return 'value' });
# And TMPL_LOOPs:
$self->param(LOOP_PARAM =>
[
{ PARAM => VALUE_FOR_FIRST_PASS, ... },
{ PARAM => VALUE_FOR_SECOND_PASS, ... }
...
]
);
4) To set the value of a a number of parameters :
# For simple TMPL_VARs:
$self->param(PARAM => 'value',
PARAM2 => 'value'
);
# And with some TMPL_LOOPs:
$self->param(PARAM => 'value',
PARAM2 => 'value',
LOOP_PARAM =>
[
{ PARAM => VALUE_FOR_FIRST_PASS, ... },
{ PARAM => VALUE_FOR_SECOND_PASS, ... }
...
],
ANOTHER_LOOP_PARAM =>
[
{ PARAM => VALUE_FOR_FIRST_PASS, ... },
{ PARAM => VALUE_FOR_SECOND_PASS, ... }
...
]
);
5) To set the value of a a number of parameters using a hash-ref :
$self->param(
{
PARAM => 'value',
PARAM2 => 'value',
LOOP_PARAM =>
[
{ PARAM => VALUE_FOR_FIRST_PASS, ... },
{ PARAM => VALUE_FOR_SECOND_PASS, ... }
...
],
ANOTHER_LOOP_PARAM =>
[
{ PARAM => VALUE_FOR_FIRST_PASS, ... },
{ PARAM => VALUE_FOR_SECOND_PASS, ... }
...
]
}
);
clear_params()
Sets all the parameters to undef. Useful internally, if nowhere else!
output()
output() returns the final result of the template. In most situations
you'll want to print this, like:
print $template->output();
When output is called each occurrence of is
replaced with the value assigned to "name" via param(). If a named
parameter is unset it is simply replaced with ''. are
evaluated once per parameter set, accumlating output on each pass.
Calling output() is guaranteed not to change the state of the Template
object, in case you were wondering. This property is mostly important
for the internal implementation of loops.
You may optionally supply a filehandle to print to automatically as the
template is generated. This may improve performance and lower memory
consumption. Example:
$template->output(print_to => *STDOUT);
The return value is undefined when using the "print_to" option.
query()
This method allow you to get information about the template structure.
It can be called in a number of ways. The simplest usage of query is
simply to check whether a parameter name exists in the template, using
the "name" option:
if ($template->query(name => 'foo')) {
# do something if a varaible of any type
# named FOO is in the template
}
This same usage returns the type of the parameter. The type is the same
as the tag minus the leading 'TMPL_'. So, for example, a TMPL_VAR
parameter returns 'VAR' from query().
if ($template->query(name => 'foo') eq 'VAR') {
# do something if FOO exists and is a TMPL_VAR
}
Note that the variables associated with TMPL_IFs and TMPL_UNLESSs will
be identified as 'VAR' unless they are also used in a TMPL_LOOP, in
which case they will return 'LOOP'.
"query()" also allows you to get a list of parameters inside a loop (and
inside loops inside loops). Example loop:
And some query calls:
# returns 'LOOP'
$type = $template->query(name => 'EXAMPLE_LOOP');
# returns ('bop', 'bee', 'example_inner_loop')
@param_names = $template->query(loop => 'EXAMPLE_LOOP');
# both return 'VAR'
$type = $template->query(name => ['EXAMPLE_LOOP', 'BEE']);
$type = $template->query(name => ['EXAMPLE_LOOP', 'BOP']);
# and this one returns 'LOOP'
$type = $template->query(name => ['EXAMPLE_LOOP',
'EXAMPLE_INNER_LOOP']);
# and finally, this returns ('inner_bee', 'inner_bop')
@inner_param_names = $template->query(loop => ['EXAMPLE_LOOP',
'EXAMPLE_INNER_LOOP']);
# for non existent parameter names you get undef
# this returns undef.
$type = $template->query(name => 'DWEAZLE_ZAPPA');
# calling loop on a non-loop parameter name will cause an error.
# this dies:
$type = $template->query(loop => 'DWEAZLE_ZAPPA');
As you can see above the "loop" option returns a list of parameter names
and both "name" and "loop" take array refs in order to refer to
parameters inside loops. It is an error to use "loop" with a parameter
that is not a loop.
Note that all the names are returned in lowercase and the types are
uppercase.
Just like "param()", "query()" with no arguements returns all the
parameter names in the template at the top level.
FREQUENTLY ASKED QUESTIONS
In the interest of greater understanding I've started a FAQ section of
the perldocs. Please look in here before you send me email.
1 Q: Is there a place to go to discuss HTML::Template and/or get help?
A: There's a mailing-list for HTML::Template at
htmltmpl@lists.vm.com. Send a blank message to
htmltmpl-subscribe@lists.vm.com to join!
2 Q: Is there a searchable archive for the mailing-list?
A: Yes, thanks to Sean P. Scanlon, there is:
http://bluedot.net/mail/archive/
3 Q: I want support for ! How about it?
A: Maybe. I definitely encourage people to discuss their ideas for
HTML::Template on the mailing list. Please be ready to explain to me
how the new tag fits in with HTML::Template's mission to provide a
fast, lightweight system for using HTML templates.
NOTE: Offering to program said addition and provide it in the form
of a patch to the most recent version of HTML::Template will
definitely have a softening effect on potential opponents!
4 Q: I found a bug, can you fix it?
A: That depends. Did you send me the VERSION of HTML::Template, a
test script and a test template? If so, then almost certainly.
If you're feeling really adventurous, HTML::Template has a
publically available CVS server. See below for more information in
the PUBLIC CVS SERVER section.
5 Q: s from the main template aren't working inside a
! Why?
A: This is the intended behavior. introduces a separate
scope for s much like a subroutine call in Perl introduces
a separate scope for "my" variables.
If you want your s to be global you can set the
'global_vars' option when you call new(). See above for
documentation of the 'global_vars' new() option.
6 Q: Why do you use /[Tt]/ instead of /t/i? It's so ugly!
A: Simple - the case-insensitive match switch is very inefficient.
According to _Mastering_Regular_Expressions_ from O'Reilly Press,
/[Tt]/ is faster and more space efficient than /t/i - by as much as
double against long strings. //i essentially does a lc() on the
string and keeps a temporary copy in memory.
When this changes, and it is in the 5.6 development series, I will
gladly use //i. Believe me, I realize [Tt] is hideously ugly.
7 Q: How can I pre-load my templates using cache-mode and mod_perl?
A: Add something like this to your startup.pl:
use HTML::Template;
use File::Find;
print STDERR "Pre-loading HTML Templates...\n";
find(
sub {
return unless /\.tmpl$/;
HTML::Template->new(
filename => "$File::Find::dir/$_",
cache => 1,
);
},
'/path/to/templates',
'/another/path/to/templates/'
);
Note that you'll need to modify the "return unless" line to specify
the extension you use for your template files - I use .tmpl, as you
can see. You'll also need to specify the path to your template
files.
One potential problem: the "/path/to/templates/" must be EXACTLY the
same path you use when you call HTML::Template->new(). Otherwise the
cache won't know they're the same file and will load a new copy -
instead getting a speed increase, you'll double your memory usage.
To find out if this is happening set cache_debug => 1 in your
application code and look for "CACHE MISS" messages in the logs.
8 Q: What characters are allowed in TMPL_* NAMEs?
A: Numbers, letters, '.', '/', '+', '-' and '_'.
9 Q: How can I execute a program from inside my template?
A: Short answer: you can't. Longer answer: you shouldn't since this
violates the fundamental concept behind HTML::Template - that design
and code should be seperate.
But, inevitably some people still want to do it. If that describes
you then you should take a look at HTML::Template::Expr. Using
HTML::Template::Expr it should be easy to write a run_program()
function. Then you can do awful stuff like:
Just, please, don't tell me about it. I'm feeling guilty enough just
for writing HTML::Template::Expr in the first place.
10 Q: Can I get a copy of these docs in Japanese?
A: Yes you can. See Kawai Takanori's translation at:
http://member.nifty.ne.jp/hippo2000/perltips/html/template.htm
11 Q: What's the best way to create a