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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 <TMPL_VAR>
For example, test.tmpl:
<HTML>
<HEAD><TITLE>Test Template</TITLE>
<BODY>
My Home Directory is <TMPL_VAR NAME=HOME>
<P>
My Path is set to <TMPL_VAR NAME=PATH>
</BODY>
</HTML>
Now create a small CGI program:
use HTML::Template;
# open the html template
my $template = HTML::Template->new(filename => 'test.tmpl');
# fill in some parameters
$template->param(
HOME => $ENV{HOME},
PATH => $ENV{PATH},
);
# send the obligatory Content-Type
print "Content-Type: text/html\n\n";
# print the template
print $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 - <TMPL_VAR>, <TMPL_LOOP>, <TMPL_INCLUDE>,
<TMPL_IF> and <TMPL_ELSE>. 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 some
one else! Using this module you fill in the values for
the variables, loops and branches declared in the tem
A Japanese translation of the documentation is available
at:
http://member.nifty.ne.jp/hippo2000/perltips/html/template.htm
This module is licensed under the GPL. See the LICENSE
section below for more details.
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 substitu
tion 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 edi
tors/analyzers to support HTML::Template.
An advantage of this module over home-grown tag-replace
ment schemes is the support for loops. In my work I am
often called on to produce tables of data in html. Pro
ducing 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
Note: even though these tags look like HTML they are a
little different in a couple of ways. First, they must
appear entirely on one line. Second, they're allowed to
"break the rules". Something like:
<IMG SRC="<TMPL_VAR NAME=IMAGE_SRC>">
The "NAME=" in the tag is optional, although for extensi
bility's sake I recommend using it. Example - "<TMPL_LOOP
LOOP_NAME>" is acceptable.
If you're a fanatic about valid HTML and would like your
templates to conform to valid HTML syntax, you may option
ally 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 pro
cessing, or who use DTD-savvy editing tools.
<!-- TMPL_VAR NAME=PARAM1 -->
In order to realize a dramatic savings in bandwidth, the
standard (non-comment) tags will be used throughout the
rest of this documentation.
<TMPL_VAR NAME="PARAMETER_NAME">
The <TMPL_VAR> tag is very simple. For each <TMPL_VAR>
tag in the template you call $template->param(PARAME
TER_NAME => "VALUE"). When the template is output the
<TMPL_VAR> 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:
<INPUT NAME=param TYPE=TEXT VALUE="<TMPL_VAR NAME="param">">
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:
<INPUT NAME=param TYPE=TEXT VALUE="<TMPL_VAR ESCAPE=HTML NAME="param">">
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'.
The <TMPL_LOOP> tag is a bit more complicated. The
<TMPL_LOOP> tag allows you to delimit a section of text
and give it a name. Inside the <TMPL_LOOP> you place
<TMPL_VAR>s. Now you pass to param() a list (an array
ref) of parameter assignments (hash refs). The loop iter
ates over this list and produces output from the text
block for each pass. Unset parameters are skipped.
Here's an example:
In the template:
<TMPL_LOOP NAME=EMPLOYEE_INFO>
Name: <TMPL_VAR NAME=NAME> <P>
Job: <TMPL_VAR NAME=JOB> <P>
<P>
</TMPL_LOOP>
In the script:
$template->param(EMPLOYEE_INFO => [
{ name => 'Sam', job => 'programmer' },
{ name => 'Steve', job => 'soda jerk' },
]
);
print $template->output();
The output:
Name: Sam <P>
Job: programmer <P>
<P>
Name: Steve <P>
Job: soda jerk <P>
<P>
As you can see above the <TMPL_LOOP> takes a list of vari
able assignments and then iterates over the loop body pro
ducing output.
Often you'll want to generate a <TMPL_LOOP>'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
$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:
<TMPL_LOOP NAME="THIS_LOOP">
Word: <TMPL_VAR NAME="WORD"><BR>
Number: <TMPL_VAR NAME="NUMBER"><P>
</TMPL_LOOP>
It would produce output like:
Word: I
Number: 1
Word: Am
Number: 2
Word: Cool
Number: 3
<TMPL_LOOP>s within <TMPL_LOOP>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('ROW',[
{ name => 'Bobby',
nicknames => [
{ name => 'the big bad wolf' },
{ name => 'He-Man' },
],
},
],
);
Basically, each <TMPL_LOOP> 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 <TMPL_LOOP>, the only variables that are usable
are the ones from the <TMPL_LOOP>. The variables in the
outer blocks are not visible within a template loop. For
If you want your variables to be global you can use
'global_vars' option to new described below.
<TMPL_INCLUDE NAME="filename.tmpl">
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 con
tents were physically included in the master template.
The file specified can be a full path - beginning with a
'/'. If it isn't a full path, the path to the enclosing
file is tried first. After that the path in the environ
ment variable HTML_TEMPLATE_ROOT is tried next, if it
exists. Next, the "path" new() 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 NAME="CONTROL_PARAMETER_NAME"> </TMPL_IF>
The <TMPL_IF> tag allows you to include or not include a
block of the template based on the value of a given param
eter 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 speci
fied the same way as with TMPL_VAR.
Example Template:
<TMPL_IF NAME="BOOL">
Some text that only gets displayed if BOOL is true!
</TMPL_IF>
Now if you call $template->param(BOOL => 1) then the above
block will be included by output.
<TMPL_IF> </TMPL_IF> blocks can include any valid
HTML::Template construct - VARs and LOOPs and other
IF/ELSE blocks. Note, however, that intersecting a
<TMPL_IF> and a <TMPL_LOOP> is invalid.
<TMPL_IF BOOL>
<TMPL_LOOP SOME_LOOP>
</TMPL_IF>
</TMPL_LOOP>
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. Exam
ple:
<TMPL_IF LOOP_ONE>
This will output if the loop is not empty.
</TMPL_IF>
<TMPL_LOOP LOOP_ONE>
....
</TMPL_LOOP>
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 syn
chronized. 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
</TMPL_IF>, not </TMPL_ELSE>!
Example:
<TMPL_IF BOOL>
Some text that is included only if BOOL is true
<TMPL_ELSE>
Some text that is included only if BOOL is false
</TMPL_IF>
<TMPL_UNLESS NAME="CONTROL_PARAMETER_NAME"> </TMPL_UNLESS>
This tag is the opposite of <TMPL_IF>. The block is out
put if the CONTROL_PARAMETER is set false or not defined.
You can use <TMPL_ELSE> with <TMPL_UNLESS> just as you can
with <TMPL_IF>.
Example:
Some text that is output only if BOOL is FALSE.
<TMPL_ELSE>
Some text that is output only if BOOL is TRUE.
</TMPL_UNLESS>
If the name of a TMPL_LOOP is used in a TMPL_UNLESS, the
UNLESS block output if the loop has zero rows.
<TMPL_UNLESS LOOP_ONE>
This will output if the loop is empty.
</TMPL_UNLESS>
<TMPL_LOOP LOOP_ONE>
....
</TMPL_LOOP>
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.
The three new() calling methods can also be accessed as
below, if you prefer.
my $t = HTML::Template->new_file('file.tmpl', option => 'value');
option => 'value');
my $t = HTML::Template->new_array_ref($ref_to_array_of_lines,
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:
· 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:
<TMPL_HUH NAME=ZUH>
Would normally cause an error, but if you call new
with strict => 0, HTML::Template will ignore it.
Defaults to 1.
· 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 speci
fied, not scalarref or arrayref templates. Caching
also looks at the modification times of any files
included using <TMPL_INCLUDE> 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
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 modifica
tion 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% perfor
mance 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 mod
ule (available from CPAN). The effect of this will be
to maintain a single shared copy of each parsed tem
plate 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 main
tain 25 httpd processes - shared_cache results in sav
ing almost 100MB! Of course, some reduction in speed
versus normal caching is to be expected. Another dif
ference between normal caching and shared_cache is
that shared_cache will work in a CGI environment -
normal caching is only useful in a persistent environ
ment 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_seg
ment_size and ipc_max_size. See the IPC::SharedCache
manpage 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 the IPC::SharedCache
manpage.
· double_cache - if set to 1 the module will use a com
bination 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
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 filesys
tem (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 direc
tory. 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 inconve
nient 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.
· 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'));
be provided by the $cgi->param() method. Parameters
you set directly take precedence over associated
parameters.
You can specify multiple objects to associate by pass
ing 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-insen
sitve manner. If you have two parameters in a CGI
object like 'NAME' and 'Name' one will be chosen ran
domly 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 <TMPL_IF>,
<TMPL_UNLESS> and <TMPL_ELSE> to control how a loop is
output. Example:
<TMPL_LOOP NAME="FOO">
<TMPL_IF NAME="__FIRST__">
This only outputs on the first pass.
</TMPL_IF>
<TMPL_IF NAME="__ODD__">
This outputs every other pass, on the odd passes.
</TMPL_IF>
<TMPL_UNLESS NAME="__ODD__">
This outputs every other pass, on the even passes.
This outputs on passes that are neither first nor last.
</TMPL_IF>
<TMPL_IF NAME="__LAST__">
This only outputs on the last pass.
<TMPL_IF>
</TMPL_LOOP>
One use of this feature is to provide a "separator"
similar in effect to the perl function join(). Exam
ple:
<TMPL_LOOP FRUIT>
<TMPL_IF __LAST__> and </TMPL_IF>
<TMPL_VAR KIND><TMPL_UNLESS __LAST__>, <TMPL_ELSE>.</TMPL_UNLESS>
</TMPL_LOOP>
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__.
· 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
<TMPL_INCLUDE> 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 <TMPL_INCLUDE> 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
('/').
· no_includes - set this option to 1 to disallow the
<TMPL_INCLUDE> tag in the template file. This can be
used to make opening untrusted templates slightly less
dangerous. Defaults to 0.
imum 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.
· 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 <TMPL_INCLUDE>
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.
· global_vars - normally variables declared outside a
loop are not available inside a loop. This option
makes <TMPL_VAR>s like global variables in Perl - they
have unlimited scope. This option also affects
<TMPL_IF> and <TMPL_UNLESS>.
Example:
This is a normal variable: <TMPL_VAR NORMAL>.<P>
<TMPL_LOOP NAME=FROOT_LOOP>
Here it is inside the loop: <TMPL_VAR NORMAL><P>
</TMPL_LOOP>
Normally this wouldn't work as expected, since
<TMPL_VAR NORMAL>'s value outside the loop is not
available inside the loop.
· 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_(.*?)!!!/<TMPL_$1>/g;
}
# open zap.tmpl using the above filter
my $template = HTML::Template->new(filename => 'zap.tmpl',
filter => $filter);
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".
my $template = HTML::Template->new(filename => 'zap.tmpl',
filter => { sub => $filter,
format => 'array' });
Using the 'array' format is likely to be more effi
cient since this is how HTML::Template stores the tem
plate text internally. This may change in the future.
You may also have multiple filters. This allows sim
ple filters to be combined for more elaborate func
tionality. To do this you specify an array of fil
ters. 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.
· vanguard_compatibility_mode - if set to 1 the module
will expect to see <TMPL_VAR>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.
· 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 infor
mation on cache loads, hits and misses to STDERR.
Defaults to 0.
· shared_cache_debug - if set to 1 the module will turn
· memory_debug - if set to 1 the module will send infor
mation on cache memory usage to STDERR. Requires the
GTop module. Defaults to 0.
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.
$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'
);
$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 <TMPL_VAR
replaced with ''. <TMPL_LOOPS> 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 implementa
tion of loops.
You may optionally supply a filehandle to print to auto
matically as the template is generated. This may improve
performance and lower memory consumption. Example:
$template->output(print_to => *STDOUT);
The return value is undefined when using the "print_to"
option.
query()
This method allow you to get information about the tem
plate structure. It can be called in a number of ways.
The simplest usage of query is simply to check whether a
parameter name exists in the template, using the `name'
option:
if ($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:
<TMPL_VAR NAME="BEE">
<TMPL_VAR NAME="BOP">
<TMPL_LOOP NAME="EXAMPLE_INNER_LOOP">
<TMPL_VAR NAME="INNER_BEE">
<TMPL_VAR NAME="INNER_BOP">
</TMPL_LOOP>
</TMPL_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.
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) I want support for <TMPL_XXX>! How about it?
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!
3) I found a bug, can you fix it?
That depends. Did you send me the VERSION of HTML::Tem
plate, 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.
4) <TMPL_VAR>s from the main template aren't working
inside a <TMPL_LOOP>! Why?
This is the intended behavior. <TMPL_LOOP> introduces a
separate scope for <TMPL_VAR>s much like a subroutine call
in Perl introduces a separate scope for "my" variables.
If you want your <TMPL_VAR>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.
5) Why do you use /[Tt]/ instead of /t/i? It's so ugly!
Simple - the case-insensitive match switch is very ineffi
cient. 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 tem
porary 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.
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::Tem
plate->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.
7) What characters are allowed in TMPL_* NAMEs?
Numbers, letters, '.', '/', '+', '-' and '_'.
8) How can I execute a program from inside my template?
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. At times
it has even seemed that HTML::Template development might
split over this issue, so I will attempt a compromise.
Here is a method you can use to allow your template
authors to evaluate arbitrary perl scripts from within the
template.
First, tell all your designers that when they want to run
a perl script named "program.pl" they should use a tag
Then, have all your programmers call this subroutine
instead of calling HTML::Template::new directly. They
still use the same parameters, but they also get the pro
gram execution.
sub new_template {
# get the template object
my $template = HTML::Template->new(@_);
# find program parameters and fill them in
my @params = $template->param();
for my $param (@params) {
if ($param =~ /^__execute_(.*)__$/) {
$template->param($param, do($1));
}
}
# return the template object
return $template;
}
The programs called in this way should return a string
containing their output. A more complicated subroutine
could be written to capture STDOUT from the scripts, but
this one is simple enough to include in the FAQ. Another
improvement would be to use query() to enable program exe
cution inside loops.
9) Can I get a copy of these docs in Japanese?
Yes you can. See Kawai Takanori's translation at:
http://member.nifty.ne.jp/hippo2000/perltips/html/template.htm
BUGS
I am aware of no bugs - if you find one, join the mailing
list and tell us about it (htmltmpl@lists.vm.com). You
can join the HTML::Template mailing-list by sending a
blank email to htmltmpl-subscribe@lists.vm.com. Of
course, you can still email me directly (sam@tregar.com)
with bugs, but I reserve the right to forward bug reports
to the mailing list.
When submitting bug reports, be sure to include full
details, including the VERSION of the module, a test
script and a test template demonstrating the problem!
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.
This module was the brain child of my boss, Jesse Erlbaum
(jesse@vm.com) here at Vanguard Media. The most original
idea in this module - the <TMPL_LOOP> - was entirely his.
Fixes, Bug Reports, Optimizations and Ideas have been gen
erously provided by:
Richard Chen
Mike Blazer
Adriano Nagelschmidt Rodrigues
Andrej Mikus
Ilya Obshadko
Kevin Puetz
Steve Reppucci
Richard Dice
Tom Hukins
Eric Zylberstejn
David Glasser
Peter Marelas
James William Carlson
Frank D. Cringle
Winfried Koenig
Matthew Wickline
Doug Steinwand
Drew Taylor
Tobias Brox
Michael Lloyd
Simran Gambhir
Chris Houser <chouser@bluweb.com>
Larry Moore
Todd Larason
Jody Biggs
T.J. Mather
Martin Schroth
Dave Wolfe
uchum
Kawai Takanori
Peter Guelich
Chris Nokleberg
Ralph Corderoy
William Ward
Ade Olonoh
Mark Stosberg
Thanks!
PUBLIC CVS SERVER
HTML::Template now has a publicly accessible CVS server
provided by SourceForge (www.sourceforge.net). You can
access it by going to http://source
forge.net/cvs/?group_id=1075. Give it a try!
Sam Tregar, sam@tregar.com (you can also find me on the
mailing list at htmltmpl@lists.vm.com - join it by sending
a blank message to htmltmpl-subscribe@lists.vm.com).
LICENSE
HTML::Template : A module for using HTML Templates with
Perl Copyright (C) 2000 Sam Tregar (sam@tregar.com)
This module is free software; you can redistribute it
and/or modify it under the terms of either:
a) the GNU General Public License as published by the Free
Software Foundation; either version 1, or (at your option)
any later version, or
b) the "Artistic License" which comes with this module.
This program is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See either the GNU General Public License or the
Artistic License for more details.
You should have received a copy of the Artistic License
with this module, in the file ARTISTIC. If not, I'll be
glad to provide one.
You should have received a copy of the GNU General Public
License along with this program; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330,
Boston, MA 02111-1307 USA