mustache.5.ron

mustache(5) -- Logic-less templates.
====================================

## SYNOPSIS

A typical Mustache template:

    Hello {{name}}
    You have just won {{value}} dollars!
    {{#in_ca}}
    Well, {{taxed_value}} dollars, after taxes.
    {{/in_ca}}

Given the following hash:

    {
      "name": "Chris",
      "value": 10000,
      "taxed_value": 10000 - (10000 * 0.4),
      "in_ca": true
    }

Will produce the following:

    Hello Chris
    You have just won 10000 dollars!
    Well, 6000.0 dollars, after taxes.


## DESCRIPTION

Mustache can be used for HTML, config files, source code -
anything. It works by expanding tags in a template using values
provided in a hash or object.

We call it "logic-less" because there are no if statements, else
clauses, or for loops. Instead there are only tags. Some tags are
replaced with a value, some nothing, and others a series of
values. This document explains the different types of Mustache tags.

The Mustache language has a [formal specification][spec]. The current
manpage reflects version 1.3.0 of the specification, including the
official-but-optional extensions for lambdas and inheritance.

[spec]: https://github.com/mustache/spec


## TAG TYPES

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, the parent contexts will be checked recursively.
If the top context is reached and the `name` key is still not found,
nothing will be rendered.

All variables are HTML escaped by default. If you want to return raw contents
without escaping, use the triple mustache: `{{{name}}}`.

You can also use `&` to return its raw contents: `{{& name}}`. This may be
useful when changing delimiters (see "Set Delimiter" below).

By default a variable "miss" returns an empty string. This can usually
be configured in your Mustache library. The Ruby version of Mustache
supports raising an exception in this situation, for instance.

Template:

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

Hash:

    {
      "name": "Chris",
      "company": "<b>GitHub</b>"
    }

Output:

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

**Dotted Names**

If the `name` contains dots, it is split on the dots to obtain multiple
keys. The first key is looked up in the context as described above. If it
is found, the next key is looked up within the previous result. This is
repeated until a key is not found or until the last key is found. The
final result is interpolated as above.

Template:

    * {{client.name}}
    * {{age}}
    * {{client.company.name}}
    * {{{company.name}}}

Hash:

    {
      "client": {
        "name": "Chris & Friends",
        "age": 50
      },
      "company": {
        "name": "<b>GitHub</b>"
      }
    }

Output:

    * Chris &amp; Friends
    *
    *
    * <b>GitHub</b>

**Implicit Iterator**

As a special case, if the `name` consists of only a dot and nothing else,
the value that is the current context is interpolated as a whole. This
is especially useful if the parent context is a list; see **Sections**
below.

Template:

    * {{.}}

Current context:

    "Hello!"

Output:

    * Hello!

**Lambdas**

If any value found during the lookup is a callable object, such as a
function or lambda, this object will be invoked with zero arguments. The
value that is returned is then used instead of the callable object itself.

An **optional** part of the specification states that if the final key in
the `name` is a lambda that returns a string, then that string should be
rendered as a Mustache template before interpolation. It will be rendered
using the default delimiters (see **Set Delimiter** below) against the
current context.

Template:

    * {{time.hour}}
    * {{today}}

Hash:

    {
      "year": 1970,
      "month": 1,
      "day": 1,
      "time": function() {
        return {
          "hour": 0,
          "minute": 0,
          "second": 0
        }
      },
      "today": function() {
        return "{{year}}-{{month}}-{{day}}"
      }
    }

Output:

    * 0
    * 1970-1-1


### Sections

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

Lookup of dotted names works in the same way as with variables, except for
slightly different treatment of lambdas. More on this below.

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 final value of the key
lookup.

**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.
    {{#person}}
      Never shown!
    {{/person}}

Hash:

    {
      "person": false
    }

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}}

Hash:

    {
      "repo": [
        { "name": "resque" },
        { "name": "hub" },
        { "name": "rip" }
      ]
    }

Output:

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

The same effect as above can be obtained without nested objects, by using
the implicit iterator (see **Variables** above).

Template:

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

Hash:

    {
      "repo": ["resque", "hub", "rip"]
    }

Output:

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

**Lambdas**

When any value found during the lookup is a callable object, such as a
function or lambda, the object will be invoked and passed the block of
text. The text passed is the literal block, unrendered. `{{tags}}` will
not have been expanded.

An **optional** part of the specification states that if the final key in
the `name` is a lambda that returns a string, then that string replaces
the content of the section. It will be rendered using the same delimiters
(see **Set Delimiter** below) as the original section content. In this way
you can implement filters or caching.

Template:

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

Hash:

    {
      "name": "Willy",
      "wrapped": function(text) {
        return "<b>" + text + "</b>"
      }
    }

Output:

    <b>Willy is awesome.</b>

**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?}}

Hash:

    {
      "person?": { "name": "Jon" }
    }

Output:

      Hi Jon!


### 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 zero 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}}

Hash:

    {
      "repo": []
    }

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. Whereas in ERB you may have
this:

    <%= partial :next_more, :start => start, :size => size %>

Mustache requires only this:

    {{> next_more}}

Why? Because the `next_more.mustache` file will inherit the `size` and
`start` methods from 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 and partial:

    base.mustache:
    <h2>Names</h2>
    {{#names}}
      {{> user}}
    {{/names}}

    user.mustache:
    <strong>{{name}}</strong>

Can be thought of as a single, expanded template:

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


**Dynamic Names**

Partials can be loaded dynamically at runtime using Dynamic Names; an
**optional** part of the Mustache specification which allows to dynamically
determine a tag's content at runtime.

Dynamic Names consists of an asterisk, followed by a dotted name which follows
the same notation and the same resolution as in an variable tag. That is
`{{>*dynamic}}`. It can be thought as the following **hypothetical** tag
(which is **not allowed**!): `{{>{{dynamic}}}}`.

Templates:

    main.mustache:
    Hello {{>*dynamic}}
    
    world.template:
    everyone!

Hash:

    {
      "dynamic": "world"
    }

Output:

    Hello everyone!


### Blocks

A block begins with a dollar and ends with a slash. That is, `{{$title}}`
begins a "title" block and `{{/title}}` ends it.

Blocks mark parts of the template that may be overridden. This can be done
with a block of the same name within a parent section in the calling
template (see **Parents** below). If not overridden, the contents of a
block render just as if the `{{$title}}` and `{{/title}}` tags weren't
there.

Blocks could be thought of as template parameters or as inline partials
that may be passed to another template. They are part of the optional
inheritance extension.

Template `article.mustache`:

    <h1>{{$title}}The News of Today{{/title}}</h1>
    {{$body}}
    <p>Nothing special happened.</p>
    {{/body}}

Output:

    <h1>The News of Today</h1>
    <p>Nothing special happened.</p>


### Parents

A parent begins with a less than sign and ends with a slash. That is,
`{{<article}}` begins an "article" parent and `{{/article}}` ends it.

Like an `{{>article}}` partial, a parent lets you expand another template
inside the current one. Unlike a partial, a parent also lets you override
blocks of the other template.

Blocks within a parent can again be overridden by another including
template. Other content within a parent is ignored, like comments.

Template:

    {{<article}}
      Never shown
      {{$body}}
        {{#headlines}}
        <p>{{.}}</p>
        {{/headlines}}
      {{/body}}
    {{/article}}

    {{<article}}
      {{$title}}Yesterday{{/title}}
    {{/article}}

Hash:

    {
      "headlines": [
        "A pug's handler grew mustaches.",
        "What an exciting day!"
      ]
    }

Output, assuming the `article.mustache` from before:

    <h1>The News of Today</h1>
    <p>A pug's handler grew mustaches.</p>
    <p>What an exciting day!</p>

    <h1>Yesterday</h1>
    <p>Nothing special happened.</p>

**Dynamic Names**

Some mustache implementations may allow the use of Dynamic Names in
parent tags, similar to dynamic names in partials. Here's an example of
how Dynamic Names in parent tags work.

Templates:

    {{!normal.mustache}}
    {{$text}}Here goes nothing.{{/text}}

    {{!bold.mustache}}
    <b>{{$text}}Here also goes nothing but it's bold.{{/text}}</b>

    {{!dynamic.mustache}}
    {{<*dynamic}}
      {{$text}}Hello World!{{/text}}
    {{/*dynamic}}

Hash:

    {
      "dynamic": "bold"
    }

Output:

    <b>Hello World!</b>


### 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][ct], 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.

[ct]: http://goog-ctemplate.sourceforge.net/doc/howto.html


## COPYRIGHT

Mustache is Copyright (C) 2009 Chris Wanstrath

Original CTemplate by Google


## SEE ALSO

mustache(1),
<http://mustache.github.io/>