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<h1 class="headline">Template::Manual::VMethods</h1>
<h2 class="subhead">Virtual Methods</h1>
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<h1 id="contents" onclick="switch_section(this)" title="Click title to show/hide section content.">Contents</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<ul class="toc">
<li class=""><a href="#Scalar_Virtual_Methods">Scalar Virtual Methods</a></li>
<li class="sub"><a href="#section_defined">defined</a></li>
<li class="sub"><a href="#section_length">length</a></li>
<li class="sub"><a href="#method_repeat">repeat(n)</a></li>
<li class="sub"><a href="#method_replace">replace(search, replace)</a></li>
<li class="sub"><a href="#method_remove">remove(pattern)</a></li>
<li class="sub"><a href="#method_match">match(pattern, global)</a></li>
<li class="sub"><a href="#method_search">search(pattern)</a></li>
<li class="sub"><a href="#method_split">split(pattern)</a></li>
<li class="sub"><a href="#method_chunk">chunk(size)</a></li>
<li class="sub"><a href="#method_substr">substr(offset, length, replacement)</a></li>
<li class="sub"><a href="#section_list">list</a></li>
<li class="sub"><a href="#section_hash_">hash </a></li>
<li class="sub"><a href="#section_size">size</a></li>
<li class=""><a href="#Hash_Virtual_Methods">Hash Virtual Methods</a></li>
<li class="sub"><a href="#section_keys">keys</a></li>
<li class="sub"><a href="#section_values">values</a></li>
<li class="sub"><a href="#section_items">items</a></li>
<li class="sub"><a href="#section_each">each</a></li>
<li class="sub"><a href="#section_pairs_">pairs </a></li>
<li class="sub"><a href="#section_list">list</a></li>
<li class="sub"><a href="#section_sort_nsort">sort, nsort</a></li>
<li class="sub"><a href="#section_import">import</a></li>
<li class="sub"><a href="#section_defined_exists">defined, exists</a></li>
<li class="sub"><a href="#section_delete_">delete </a></li>
<li class="sub"><a href="#section_size">size</a></li>
<li class="sub"><a href="#section_item">item</a></li>
<li class=""><a href="#List_Virtual_Methods">List Virtual Methods</a></li>
<li class="sub"><a href="#section_first_last">first, last</a></li>
<li class="sub"><a href="#section_size_max">size, max</a></li>
<li class="sub"><a href="#section_defined">defined</a></li>
<li class="sub"><a href="#section_reverse">reverse</a></li>
<li class="sub"><a href="#section_join">join</a></li>
<li class="sub"><a href="#section_grep">grep</a></li>
<li class="sub"><a href="#section_sort_nsort">sort, nsort</a></li>
<li class="sub"><a href="#method_unshift_item_push">unshift(item), push(item)</a></li>
<li class="sub"><a href="#section_shift_pop">shift, pop</a></li>
<li class="sub"><a href="#section_unique">unique</a></li>
<li class="sub"><a href="#section_import">import</a></li>
<li class="sub"><a href="#section_merge">merge</a></li>
<li class="sub"><a href="#method_slice">slice(from, to)</a></li>
<li class="sub"><a href="#method_splice">splice(offset, length, list)</a></li>
<li class="sub"><a href="#section_hash_">hash </a></li>
<li class=""><a href="#Automagic_Promotion_of_Scalar_to_List_for_Virtual_Methods">Automagic Promotion of Scalar to List for Virtual Methods</a></li>
<li class=""><a href="#Defining_Custom_Virtual_Methods">Defining Custom Virtual Methods</a></li>
</ul>
</div>
</div>
<div class="pod">
<div class="section">
<div class="head">
<h1 id="Scalar_Virtual_Methods" onclick="switch_section(this)" title="Click title to show/hide section content.">Scalar Virtual Methods</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<div class="subsection">
<div class="head">
<h2 id="section_defined" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">defined</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns true if the value is defined.
</p>
<pre>[% user = get_user(uid) IF uid.defined %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_length" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">length</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns the length of the string representation of the item:
</p>
<pre>[% IF password.length < 8 %]
Password too short, dumbass!
[% END %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="method_repeat" class="method" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">repeat(n)</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Repeat the string a specified number of times.
</p>
<pre>[% name = 'foo' %]
[% name.repeat(3) %] # foofoofoo</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="method_replace" class="method" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">replace(search, replace)</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Outputs the string with all instances of the first argument (specified as
a Perl regular expression) with the second.
</p>
<pre>[% name = 'foo, bar & baz' %]
[% name.replace('\W+', '_') %] # foo_bar_baz</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="method_remove" class="method" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">remove(pattern)</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Outputs the string with all instances of the pattern (specified as a Perl
regular expression) removed.
</p>
<pre>[% name = 'foo, bar & baz' %]
[% name.remove('\W+') %] # foobarbaz</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="method_match" class="method" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">match(pattern, global)</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Performs a regular expression match on the string using the pattern
passed as an argument. If the pattern matches the string then the method
returns a reference to a list of any strings captured within parenthesis
in the pattern.
</p>
<pre>[% name = 'Larry Wall' %]
[% matches = name.match('(\w+) (\w+)') %]
[% matches.1 %], [% matches.0 %] # Wall, Larry</pre>
<p>
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.
</p>
<pre>[% "We're not worthy!" IF name.match('Larry Wall') %]</pre>
<pre>[% IF (matches = name.match('(\w+) (\w+)')) %]
pattern matches: [% matches.join(', ') %]
[% ELSE %]
pattern does not match
[% END %]</pre>
<p>
Any regex modifiers, like <code>/s</code>, should be added in the regex
using the <code>(?s)</code> syntax. For example, to modify the regex to
disregard whitespace (the <code>/x</code> switch), use:
</p>
<pre>[% re = '(?x)
(\w+)
[ ]
(\w+)
';
matches = name.match(re);
%]</pre>
<p>
To perform a global search to match the pattern as many times as it
appears in the source string, provide a true value for the
<code>global</code> argument following the pattern.
</p>
<pre>[% text = 'bandanna';
text.match('an+', 1).join(', ) # an, ann
%]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="method_search" class="method" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">search(pattern)</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Performs a similar function to <a href="#section_match">match</a> but
simply returns true if the string matches the regular expression pattern
passed as an argument.
</p>
<pre>[% name = 'foo bar baz' %]
[% name.search('bar') ? 'bar' : 'no bar' %] # bar</pre>
<p>
This virtual method is now deprecated in favour of <a
href="#section_match">match</a>. Move along now, there's nothing more to
see here.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="method_split" class="method" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">split(pattern)</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Calls Perl's <code>split()</code> function to split a string into a list
of strings.
</p>
<pre>[% FOREACH dir IN mypath.split(':') %]
[% dir %]
[% END %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="method_chunk" class="method" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">chunk(size)</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Splits the value into a list of chunks of a certain size.
</p>
<pre>[% ccard_no = "1234567824683579";
ccard_no.chunk(4).join
%]</pre>
<p>
Output:
</p>
<pre>1234 5678 2468 3579</pre>
<p>
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.
</p>
<pre>[% number = 1234567;
number.chunk(-3).join(',')
%]</pre>
<p>
Output:
</p>
<pre>1,234,567</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="method_substr" class="method" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">substr(offset, length, replacement)</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns a substring starting at <code>offset</code>, for
<code>length</code> characters.
</p>
<pre>[% str 'foo bar baz wiz waz woz') %]
[% str.substr(4, 3) %] # bar</pre>
<p>
If <code>length</code> is not specified then it returns everything from
the <code>offset</code> to the end of the string.
</p>
<pre>[% str.substr(12) %] # wiz waz woz</pre>
<p>
If both <code>length</code> and <code>replacement</code> are specified,
then the method replaces everything from <code>offset</code> for
<code>length</code> characters with <code>$replacement</code>. The
substring removed from the string is then returned.
</p>
<pre>[% str.substr(0, 11, 'FOO') %] # foo bar baz
[% str %] # FOO wiz waz woz</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_list" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">list</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Return the value as a single element list. This can be useful if you have
a variable which may contain a single item or a list and you want to
treat them equally. The <code>list</code> method can be called against a
list reference and will simply return the original reference, effectively
a no-op.
</p>
<pre>[% thing.list.size %] # thing can be a scalar or a list</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_hash_" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">hash </h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Return the value as a hash reference containing a single entry with the
key <code>value</code> indicating the original scalar value. As with the
<code>list</code> virtual method, this is generally used to help massage
data into different formats.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_size" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">size</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Always returns 1 for scalar values. This method is provided for
consistency with the hash and list size methods.
</p>
</div>
</div>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="Hash_Virtual_Methods" onclick="switch_section(this)" title="Click title to show/hide section content.">Hash Virtual Methods</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<div class="subsection">
<div class="head">
<h2 id="section_keys" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">keys</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns a list of keys in the hash. They are not returned in any
particular order, but the order is the same as for the corresponding
values method.
</p>
<pre>[% FOREACH key IN hash.keys %]
* [% key %]
[% END %]</pre>
<p>
If you want the keys in sorted order, use the list <code>sort</code>
method.
</p>
<pre>[% FOREACH key IN hash.keys.sort %]
* [% key %]
[% END %]</pre>
<p>
Having got the keys in sorted order, you can then use variable
interpolation to fetch the value. This is shown in the following example
by the use of <code>$key</code> to fetch the item from <code>hash</code>
whose key is stored in the <code>key</code> variable.
</p>
<pre>[% FOREACH key IN hash.keys.sort %]
* [% key %] = [% hash.$key %]
[% END %]</pre>
<p>
Alternately, you can use the <code>pairs</code> method to get a list of
key/value pairs in sorted order.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_values" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">values</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns a list of the values in the hash. As with the <code>keys</code>
method, they are not returned in any particular order, although it is the
same order that the keys are returned in.
</p>
<pre>[% hash.values.join(', ') %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_items" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">items</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns a list of both the keys and the values expanded into a single
list.
</p>
<pre>[% hash = {
a = 10
b = 20
};
hash.items.join(', ') # a, 10, b, 20
%]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_each" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">each</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
This method currently returns the same thing as the <code>items</code>
method.
</p>
<p>
However, please note that this method will change in the next major
version of the Template Toolkit (v3) to return the same thing as the
<code>pairs</code> method. This will be done in an effort to make these
virtual method more consistent with each other and how Perl works.
</p>
<p>
In anticipation of this, we recommend that you stop using
<code>hash.each</code> and instead use <code>hash.items</code>.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_pairs_" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">pairs </h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
This method returns a list of key/value pairs. They are returned in
sorted order according to the keys.
</p>
<pre>[% FOREACH pair IN product.pairs %]
* [% pair.key %] is [% pair.value %]
[% END %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_list" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">list</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns the contents of the hash in list form. An argument can be passed
to indicate the desired items required in the list: <code>keys</code> to
return a list of the keys (same as <code>hash.keys</code>),
<code>values</code> to return a list of the values (same as
<code>hash.values</code>), <code>each</code> to return as list of key and
values (same as <code>hash.each</code>), or <code>pairs</code> to return
a list of key/value pairs (same as <code>hash.pairs</code>).
</p>
<pre>[% keys = hash.list('keys') %]
[% values = hash.list('values') %]
[% items = hash.list('each') %]
[% pairs = hash.list('pairs') %]</pre>
<p>
When called without an argument it currently returns the same thing as
the <code>pairs</code> method. However, please note that this method will
change in the next major version of the Template Toolkit (v3) to return a
reference to a list containing the single hash reference (as per the
scalar list method).
</p>
<p>
In anticipation of this, we recommend that you stop using
<code>hash.list</code> and instead use <code>hash.pairs</code>.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_sort_nsort" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">sort, nsort</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Return a list of the keys, sorted alphabetically (<code>sort</code>) or
numerically (<code>nsort</code>) according to the corresponding values in
the hash.
</p>
<pre>[% FOREACH n IN phones.sort %]
[% phones.$n %] is [% n %],
[% END %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_import" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">import</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>import</code> method can be called on a hash array to import
the contents of another hash array.
</p>
<pre>[% hash1 = {
foo = 'Foo'
bar = 'Bar'
}
hash2 = {
wiz = 'Wiz'
woz = 'Woz'
}
%]
[% hash1.import(hash2) %]
[% hash1.wiz %] # Wiz</pre>
<p>
You can also call the <code>import()</code> method by itself to import a
hash array into the current namespace hash.
</p>
<pre>[% user = { id => 'lwall', name => 'Larry Wall' } %]
[% import(user) %]
[% id %]: [% name %] # lwall: Larry Wall</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_defined_exists" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">defined, exists</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns a true or false value if an item in the hash denoted by the key
passed as an argument is defined or exists, respectively.
</p>
<pre>[% hash.defined('somekey') ? 'yes' : 'no' %]
[% hash.exists('somekey') ? 'yes' : 'no' %]</pre>
<p>
When called without any argument, <code>hash.defined</code> returns true
if the hash itself is defined (e.g. the same effect as
<code>scalar.defined</code>).
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_delete_" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">delete </h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Delete one or more items from the hash.
</p>
<pre>[% hash.delete('foo', 'bar') %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_size" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">size</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns the number of key/value pairs in the hash.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_item" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">item</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns an item from the hash using a key passed as an argument.
</p>
<pre>[% hash.item('foo') %] # same as hash.foo</pre>
</div>
</div>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="List_Virtual_Methods" onclick="switch_section(this)" title="Click title to show/hide section content.">List Virtual Methods</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<div class="subsection">
<div class="head">
<h2 id="section_first_last" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">first, last</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns the first/last item in the list. The item is not removed from the
list.
</p>
<pre>[% results.first %] to [% results.last %]</pre>
<p>
If either is given a numeric argument <code>n</code>, they return the
first or last <code>n</code> elements:
</p>
<pre>The first 5 results are [% results.first(5).join(", ") %].</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_size_max" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">size, max</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns the size of a list (number of elements) and the maximum index
number (size - 1), respectively.
</p>
<pre>[% results.size %] search results matched your query</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_defined" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">defined</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns a true or false value if the item in the list denoted by the
argument is defined.
</p>
<pre>[% list.defined(3) ? 'yes' : 'no' %]</pre>
<p>
When called without any argument, <code>list.defined</code> returns true
if the list itself is defined (e.g. the same effect as
<code>scalar.defined</code>).
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_reverse" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">reverse</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns the items of the list in reverse order.
</p>
<pre>[% FOREACH s IN scores.reverse %]
...
[% END %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_join" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">join</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Joins the items in the list into a single string, using Perl's
<code>join()</code> function.
</p>
<pre>[% items.join(', ') %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_grep" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">grep</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns a list of the items in the list that match a regular expression
pattern.
</p>
<pre>[% FOREACH directory.files.grep('\.txt$') %]
...
[% END %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_sort_nsort" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">sort, nsort</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns the items in alpha (<code>sort</code>) or numerical
(<code>nsort</code>) order.
</p>
<pre>[% library = books.sort %]</pre>
<p>
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.
</p>
<pre>[% library = books.sort('author') %]</pre>
<p>
In the example, the <code>books</code> list can contains hash references
with an <code>author</code> key or objects with an <code>author</code>
method.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="method_unshift_item_push" class="method" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">unshift(item), push(item)</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
The <code>push()</code> method adds an item or items to the end of list.
</p>
<pre>[% mylist.push(foo) %]
[% mylist.push(foo, bar) %]
The C<unshift()> method adds an item or items to the start of a list.</pre>
<pre>[% mylist.unshift(foo) %]
[% mylist.push(foo, bar) %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_shift_pop" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">shift, pop</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Removes the first/last item from the list and returns it.
</p>
<pre>[% first = mylist.shift %]
[% last = mylist.pop %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_unique" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">unique</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns a list of the unique elements in a list, in the same order as in
the list itself.
</p>
<pre>[% mylist = [ 1, 2, 3, 2, 3, 4, 1, 4, 3, 4, 5 ] %]
[% numbers = mylist.unique %]</pre>
<p>
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).
</p>
<pre>[% numbers = mylist.unique.sort %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_import" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">import</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Appends the contents of one or more other lists to the end of the current
list.
</p>
<pre>[% one = [ 1 2 3 ];
two = [ 4 5 6 ];
three = [ 7 8 9 ];
one.import(two, three);
one.join(', ); # 1, 2, 3, 4, 5, 6, 7, 8, 9
%]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_merge" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">merge</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns a list composed of zero or more other lists:
</p>
<pre>[% list_one = [ 1 2 3 ];
list_two = [ 4 5 6 ];
list_three = [ 7 8 9 ];
list_four = list_one.merge(list_two, list_three);
%]</pre>
<p>
The original lists are not modified.
</p>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="method_slice" class="method" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">slice(from, to)</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns a slice of items in the list between the bounds passed as
arguments. If the second argument, <code>to</code>, isn't specified, then
it defaults to the last item in the list. The original list is not
modified.
</p>
<pre>[% first_three = list.slice(0,2) %]
[% last_three = list.slice(-3, -1) %]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="method_splice" class="method" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">splice(offset, length, list)</h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Behaves just like Perl's <code>splice()</code> function allowing you to
selectively remove and/or replace elements in a list. It removes
<code>length</code> items from the list, starting at <code>offset</code>
and replaces them with the items in <code>list</code>.
</p>
<pre>[% 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
%]</pre>
<p>
The method returns a list of the items removed by the splice. You can use
the <code>CALL</code> directive to ignore the output if you're not
planning to do anything with it.
</p>
<pre>[% CALL play_game.splice(1, 1, ping_pong) %]</pre>
<p>
As well as providing a reference to a list of replacement values, you can
pass in a list of items.
</p>
<pre>[% CALL list.splice(-1, 0, 'foo', 'bar') %]</pre>
<p>
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:
</p>
<pre>[% # 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 ]);
%]</pre>
</div>
</div> <div class="subsection">
<div class="head">
<h2 id="section_hash_" onclick="switch_subsection(this)" title="Click title to show/hide sub-section content.">hash </h2>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
Returns a reference to a hash array comprised of the elements in the
list. The even-numbered elements (0, 2, 4, etc) become the keys and the
odd-numbered elements (1, 3, 5, etc) the values.
</p>
<pre>[% list = ['pi', 3.14, 'e', 2.718] %]
[% hash = list.hash %]
[% hash.pi %] # 3.14
[% hash.e %] # 2.718</pre>
<p>
If a numerical argument is provided then the hash returned will have keys
generated for each item starting at the number specified.
</p>
<pre>[% list = ['beer', 'peanuts'] %]
[% hash = list.hash(1) %]
[% hash.1 %] # beer
[% hash.2 %] # peanuts</pre>
</div>
</div>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="Automagic_Promotion_of_Scalar_to_List_for_Virtual_Methods" onclick="switch_section(this)" title="Click title to show/hide section content.">Automagic Promotion of Scalar to List for Virtual Methods</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
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.
</p>
<p>
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.
</p>
<p>
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).
<code>Class::DBI</code> module is just one example of a particularly
useful module which returns values this way.
</p>
<p>
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.
</p>
<p>
The <code>FOREACH</code> 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 the <code>something</code>
variable is bound to a subroutine which may return one or more items:
</p>
<pre>[% FOREACH item IN something %]
...
[% END %]</pre>
<p>
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:
</p>
<pre>[% something.first %]
[% something.join %]
[% something.reverse.join(', ') %]</pre>
<p>
Note that this is very much a last-ditch behaviour. If the single item
return is an object with a <code>first</code> method, for example, then
that will be called, as expected, in preference to the list virtual
method.
</p>
</div>
</div>
<div class="section">
<div class="head">
<h1 id="Defining_Custom_Virtual_Methods" onclick="switch_section(this)" title="Click title to show/hide section content.">Defining Custom Virtual Methods</h1>
<a href="#body" class="top" title="Back up to the top of the page" >Top</a>
</div>
<div class="body">
<p>
You can define your own virtual methods for scalars, lists and hash
arrays. The <a href="../modules/Template/Stash.html">Template::Stash</a> package variables <code>$SCALAR_OPS</code>,
<code>$LIST_OPS</code> and <code>$HASH_OPS</code> are references to hash
arrays that define these virtual methods. <code>HASH_OPS</code> and
<code>LIST_OPS</code> methods are subroutines that accept a hash/list
reference as the first item. <code>SCALAR_OPS</code> 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.
</p>
<pre># 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 ];
};</pre>
<p>
Example template:
</p>
<pre>[% primes = [ 2, 3, 5, 7, 9 ] %]
[% primes.odd.join(', ') %] # 3, 5, 7, 9</pre>
<p>
TODO: document the define_vmethod() method which makes this even easier
</p>
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/manual/VMethods.html last modified 10:57:43 31-May-2007
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