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Mustache Tags

Justin Hileman edited this page · 14 revisions

Tags are indicated by the double mustaches. {{ person }} is a tag, as is {{# person }}. In both examples, we'd refer to "person" as the key or tag key. Let's talk about the different types of tags.

Variables

The most basic tag type is the variable. A {{ name }} tag in a basic template will try to find the name key in the current context. If there is no name key, nothing will be rendered.

All variables are HTML escaped by default. If you want to return unescaped HTML, use the triple mustache: {{{ name }}}.

You can also use & to unescape a variable: {{& name }}. This may be useful when changing delimiters.

By default a variable "miss" returns an empty string.

Template:

* {{ name }}
* {{ age }}
* {{ company }}
* {{{ company }}}

Data:

<?php
array(
  'name' => "Chris",
  'company' => '<b>GitHub</b>',
);

Output:

* Chris
*
* &lt;b&gt;GitHub&lt;/b&gt;
* <b>GitHub</b>

You can use dot notation to access the attributes of a variable as well:

{{ foo.bar }}

Sections

Sections render blocks of text one or more times, depending on the value of the key in the current context.

A section begins with a pound and ends with a slash. That is, {{# person }} begins a "person" section while {{/ person }} ends it.

The behavior of the section is determined by the value of the key.

Lists vs Hashes

In most languages there are two distinct array types: list and hash (or whatever you want to call them). Lists should be iterated, hashes should be treated as objects. Mustache follows this paradigm for Ruby, Javascript, Java, Python, etc.

PHP, however, treats lists and hashes as one primitive type: array. So Mustache.php needs a way to distinguish between arrays which should be iterated, and arrays which should be treated as hashes. Arrays with consecutive numeric indexes (starting with 0) are an iterable list, and anything else is treated as a section context.

False Values or Empty Lists

If the person key exists and has a value of false or an empty list, the HTML between the pound and slash will not be displayed.

Template:

Shown.
{{# nothin }}
  Never shown!
{{/ nothin }}

Data:

<?php
array(
  'person' => true,
);

Output:

Shown.

Non-Empty Lists

If the person key exists and has a non-false value, the HTML between the pound and slash will be rendered and displayed one or more times.

When the value is a non-empty list, the text in the block will be displayed once for each item in the list. The context of the block will be set to the current item for each iteration. In this way we can loop over collections.

Template:

{{# repo }}
  <b>{{ name }}</b>
{{/ repo }}

Data:

array(
  'repo' => array(
    array('name' => "resque" ),
    array('name' => "hub" ),
    array('name' => "rip" ),
  ),
);

Output:

<b>resque</b>
<b>hub</b>
<b>rip</b>

Lambdas

When the value is callable — such as an anonymous function — the callable will be invoked and passed the block of text. The text passed is the literal block, unrendered. {{ tags }} will not have been expanded. In this way you can implement filters or caching. The return value of the lambda will be rendered as if it were the original block.

Template:

{{# wrapped }}
  {{ name }} is awesome.
{{/ wrapped }}

Data:

<?php
array(
  'name' => "Willy",
  'wrapped' => function($text) {
    return "<b>" . $text . "</b>";
  }
);

Output:

<b>Willy is awesome.</b>

A Lambda Helper instance is passed to section lambdas as a second argument, giving them access to a render method which will render a string in the current context:

Template:

{{# embiggened }}
  {{ name }} is awesome.
{{/ embiggened }}

Data:

<?php
array(
  'name' => "Willy",
  'embiggened' => function($text, Mustache_LambdaHelper $helper) {
    return strtoupper($helper->render($text));
  }
);

Output:

WILLY IS AWESOME.

Non-False Values

When the value is non-false but not a list, it will be used as the context for a single rendering of the block.

Template:

{{# person? }}
  Hi {{ name }}!
{{/ person? }}

Data:

<?php
array(
    'person?' => array(
        'name' => 'Jon',
    ),
);

Output:

Hi Jon!

Implicit iterator

If the value is a non-associative array, Mustache provides an "implicit iterator" to access the current scope. It looks like this: {{ . }}.

Inside a section context, the implicit iterator refers to the current loop value:

Template:

{{# colors }}
 * {{ . }}
{{/ colors }}

Data:

<?php
array('colors' => array('red', 'blue', 'green'));

Output:

 * red
 * blue
 * green

Inverted Sections

An inverted section begins with a caret (hat) and ends with a slash. That is, {{^ person }} begins a "person" inverted section while {{/ person }} ends it.

While sections can be used to render text one or more times based on the value of the key, inverted sections may render text once based on the inverse value of the key. That is, they will be rendered if the key doesn't exist, is false, or is an empty list.

Template:

{{# repo }}
  <b>{{ name }}</b>
{{/ repo }}
{{^ repo }}
  No repos :(
{{/ repo }}

Data:

<?php
array(
    'repo' => array(),
);

Output:

No repos :(

Comments

Comments begin with a bang and are ignored. The following template:

<h1>Today{{! ignore me }}.</h1>

Will render as follows:

<h1>Today.</h1>

Comments may contain newlines.

Partials

Partials begin with a greater than sign, like {{> box }}.

Partials are rendered at runtime (as opposed to compile time), so recursive partials are possible. Just avoid infinite loops.

They also inherit the calling context. In this way you may want to think of partials as includes, or template expansion, even though it's not literally true.

For example, this template:

<h2>Names</h2>
{{# names }}
  {{> user }}
{{/ names }}

... and user partial:

<strong>{{ name }}</strong>

Can be thought of as a single, expanded template:

<h2>Names</h2>
{{# names }}
  <strong>{{ name }}</strong>
{{/ names }}

Set Delimiter

Set Delimiter tags start with an equal sign and change the tag delimiters from {{ and }} to custom strings.

Consider the following contrived example:

* {{ default_tags }}
{{=<% %>=}}
* <% erb_style_tags %>
<%={{ }}=%>
* {{ default_tags_again }}

Here we have a list with three items. The first item uses the default tag style, the second uses ERB style as defined by the Set Delimiter tag, and the third returns to the default style after yet another Set Delimiter declaration.

According to ctemplates, this "is useful for languages like TeX, where double-braces may occur in the text and are awkward to use for markup."

Custom delimiters may not contain whitespace or the equals sign.

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