|
Template::Manual::VMethods - Virtual Methods |
Template::Manual::VMethods - Virtual Methods
The Template Toolkit provides virtual methods for manipulating variable values. Most of them are analogous to regular Perl functions of the same names. This section describes the different virtual methods that can be applied to scalar, list and hash values.
[% user = get_user(uid) IF uid.defined %]
[% IF password.length < 8 %]
Password too short, dumbass!
[% END %]
repeat(n)
[% name = 'foo' %]
[% name.repeat(3) %] # foofoofoo
[% name = 'foo, bar & baz' %]
[% name.replace('\W+', '_') %] # foo_bar_baz
match(pattern)
[% name = 'Larry Wall' %]
[% matches = name.match('(\w+) (\w+)') %]
[% matches.1 %], [% matches.0 %] # Wall, Larry
If the pattern does not match then the method returns false, rather than returning an empty list which Perl and the Template Toolkit both consider to be a true value. This allows you to write expression like this.
[% "We're not worthy!" IF name.match('Larry Wall') %]
[% IF (matches = name.match('(\w+) (\w+)')) %]
pattern matches: [% matches.join(', ') %]
[% ELSE %]
pattern does not match
[% END %]
Any regex modifiers, like /s, should be added in the regex using
the (?s) syntax. For example, to modify the regex to disregard
whitespace (the /x switch), use:
[% re = '(?x)
(\w+)
[ ]
(\w+)
';
matches = name.match(re);
%]
search(pattern)
[% name = 'foo bar baz' %]
[% name.search('bar') ? 'bar' : 'no bar' %] # bar
This virtual method is now deprecated in favour of 'match'. Move along now, there's nothing more to see here.
split(pattern)split() function to split a string into a list of
strings.
[% FOREACH dir = mypath.split(':') %]
[% dir %]
[% END %]
chunk(size)
[% ccard_no = "1234567824683579";
ccard_no.chunk(4).join
%]
Output:
1234 5678 2468 3579
If the size is specified as a negative number then the text will be chunked from right-to-left. This gives the correct grouping for numbers, for example.
[% number = 1234567;
number.chunk(-3).join(',')
%]
Output:
1,234,567
[% thing.list.size %] # thing can be a scalar or a list
[% FOREACH key = product.keys %]
[% key %] => [% product.$key %]
[% END %]
[% FOREACH n = phones.sort %]
[% phones.$n %] is [% n %],
[% END %]
[% hash1 = {
foo => 'Foo',
bar => 'Bar',
}
hash2 = {
wiz => 'Wiz',
woz => 'Woz',
}
%]
[% hash1.import(hash2) %]
[% hash1.wiz %] # Wiz
You can also call the import() method by itself to import a hash array
into the current namespace hash.
[% user = { id => 'lwall', name => 'Larry Wall' } %]
[% import(user) %]
[% id %]: [% name %] # lwall: Larry Wall
[% hash.defined('somekey') ? 'yes' : 'no' %]
[% hash.exists('somekey') ? 'yes' : 'no' %]
[% hash.item('foo') %] # same as hash.foo
[% results.first %] to [% results.last %]
If either is given a numeric argument n, they return the first or
last n elements:
The first 5 results are [% results.first(5).join(", ") %].
[% results.size %] search results matched your query
[% FOREACH s = scores.reverse %]
...
[% END %]
[% items.join(', ') %]
[% FOREACH directory.files.grep('\.txt$') %]
...
[% END %]
[% library = books.sort %]
An argument can be provided to specify a search key. Where an item in the list is a hash reference, the search key will be used to retrieve a value from the hash which will then be used as the comparison value. Where an item is an object which implements a method of that name, the method will be called to return a comparison value.
[% library = books.sort('author') %]
In the example, the 'books' list can contains hash references with an 'author' key or objects with an 'author' method.
push(item)
[% mylist.unshift('prev item') %]
[% mylist.push('next item') %]
[% first = mylist.shift %]
[% last = mylist.pop %]
[% mylist = [ 1, 2, 3, 2, 3, 4, 1, 4, 3, 4, 5 ] %]
[% numbers = mylist.unique %]
While this can be explicitly sorted, it is not required that the list be sorted before the unique elements are pulled out (unlike the Unix command line utility).
[% numbers = mylist.unique.sort %]
[% list_one = [ 1 2 3 ];
list_two = [ 4 5 6 ];
list_three = [ 7 8 9 ];
list_four = list_one.merge(list_two, list_three);
%]
The original lists are not modified.
[% first_three = list.slice(0,2) %]
[% last_three = list.slice(-3, -1) %]
splice() function allowing you to selectively
remove and/or replace elements in a list. It removes 'length' items
from the list, starting at 'offset' and replaces them with the items
in 'list'.
[% play_game = [ 'play', 'scrabble' ];
ping_pong = [ 'ping', 'pong' ];
redundant = play_game.splice(1, 1, ping_pong);
redundant.join; # scrabble
play_game.join; # play ping pong
%]
The method returns a list of the items removed by the splice. You can use the CALL directive to ignore the output if you're not planning to do anything with it.
[% CALL play_game.splice(1, 1, ping_pong) %]
As well as providing a reference to a list of replacement values, you can pass in a list of items.
[% CALL list.splice(-1, 0, 'foo', 'bar') %]
Be careful about passing just one item in as a replacement value. If it is a reference to a list then the contents of the list will be used. If it's not a list, then it will be treated as a single value. You can use square brackets around a single item if you need to be explicit:
[% # push a single item, an_item
CALL list.splice(-1, 0, an_item);
# push the items from another_list
CALL list.splice(-1, 0, another_list);
# push a reference to another_list
CALL list.splice(-1, 0, [ another_list ]);
%]
In addition to the scalar virtual methods listed in the previous section, you can also call any list virtual method against a scalar. The item will be automagically promoted to a single element list and the appropriate list virtual method will be called.
One particular benefit of this comes when calling subroutines or object methods that return a list of items, rather than the preferred reference to a list of items. In this case, the Template Toolkit automatically folds the items returned into a list.
The upshot is that you can continue to use existing Perl modules or code that returns lists of items, without having to refactor it just to keep the Template Toolkit happy (by returning references to list). Class::DBI module is just one example of a particularly useful module which returns values this way.
If only a single item is returned from a subroutine then the Template Toolkit assumes it meant to return a single item (rather than a list of 1 item) and leaves it well alone, returning the single value as it is. If you're executing a database query, for example, you might get 1 item returned, or perhaps many items which are then folded into a list.
The FOREACH directive will happily accept either a list or a single item which it will treat as a list. So it's safe to write directives like this, where we assume that 'something' is bound to a subroutine which might return 1 or more items:
[% FOREACH item = something %]
...
[% END %]
The automagic promotion of scalars to single item lists means that you can also use list virtual methods safely, even if you only get one item returned. For example:
[% something.first %]
[% something.join %]
[% something.reverse.join(', ') %]
Note that this is very much a last-ditch behaviour. If the single item return is an object with a 'first' method, for example, then that will be called, as expected, in preference to the list virtual method.
You can define your own virtual methods for scalars, lists and hash arrays. The Template::Stash package variables $SCALAR_OPS, $LIST_OPS and $HASH_OPS are references to hash arrays that define these virtual methods. HASH_OPS and LIST_OPS methods are subroutines that accept a hash/list reference as the first item. SCALAR_OPS are subroutines that accept a scalar value as the first item. Any other arguments specified when the method is called will be passed to the subroutine.
# load Template::Stash to make method tables visible
use Template::Stash;
# define list method to return new list of odd numbers only
$Template::Stash::LIST_OPS->{ odd } = sub {
my $list = shift;
return [ grep { $_ % 2 } @$list ];
};
template:
[% primes = [ 2, 3, 5, 7, 9 ] %]
[% primes.odd.join(', ') %] # 3, 5, 7, 9
Andy Wardley <abw@andywardley.com>
http://www.andywardley.com/|http://www.andywardley.com/
Template Toolkit version 2.10, released on 24 July 2003.
Copyright (C) 1996-2003 Andy Wardley. All Rights Reserved. Copyright (C) 1998-2002 Canon Research Centre Europe Ltd.
This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
|
Template::Manual::VMethods - Virtual Methods |