What could be more logical awesome than no logic at all?
lustache is an implementation of the mustache template system in Lua.
Mustache is a logic-less template syntax. It 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.
For a language-agnostic overview of mustache's template syntax, see the
mustache(5) manpage.
You can use lustache to render mustache templates anywhere you can use Lua.
lustache exposes itself as a module, so you only have to require the file. and assign it.
Download lustache.lua and place it in your project, or install it with luarocks
using luarocks install lustache. On OSX, you can brew install luarocks.
Below is quick example how to use lustache:
local lustache = require "lustache"
view_model = {
title = "Joe",
calc = function ()
return 2 + 4;
end
}
output = lustache:render("{{title}} spends {{calc}}", view_model)
In this example, the lustache:render function takes two parameters: 1) the
mustache template and 2) a view_model object
that contains the data and code needed to render the template.
Lustache uses the busted testing framework.
Run luarocks make, then busted spec.
Install busted through luarocks install busted.
A mustache template is a string that contains
any number of mustache tags. Tags are indicated by the double mustaches that
surround them. {{person}} is a tag, as is {{#person}}. In both examples we
refer to person as the tag's key.
There are several types of tags available in lustache.
The most basic tag type is a simple variable. A {{name}} tag renders the value
of the name key in the current context. If there is no such key, nothing is
rendered.
All variables are HTML-escaped by default. If you want to render unescaped HTML,
use the triple mustache: {{{name}}}. You can also use & to unescape a
variable.
Template:
* {{name}}
* {{age}}
* {{company}}
* {{{company}}}
* {{&company}}
View:
{
name = "Chris",
company = "<b>GitHub</b>"
}
Output:
* Chris
*
* <b>GitHub</b>
* <b>GitHub</b>
* <b>GitHub</b>
Dot notation may be used to access keys that are properties of objects in a view.
Template:
* {{name.first}} {{name.last}}
* {{age}}
View:
{
name = {
first = "Michael",
last = "Jackson"
},
age = "RIP"
}
Output:
* Michael Jackson
* RIP
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 text between the two
tags is referred to as that section's "block".
The behavior of the section is determined by the value of the key.
If the person key exists and has a value of null, undefined, or false,
or is an empty list, the block will not be rendered.
Template:
Shown.
{{#person}}
Never shown!
{{/person}}
View:
{
person = false
}
Output:
Shown.
If the person key exists and is not null, undefined, or false, and is
not an empty list the block will be rendered one or more times.
When the value is a list, the block is rendered once for each item in the list. The context of the block is set to the current item in the list for each iteration. In this way we can loop over collections.
Template:
{{#stooges}}
<b>{{name}}</b>
{{/stooges}}
View:
{
stooges = [
{ name = "Moe" },
{ name = "Larry" },
{ name = "Curly" }
]
}
Output:
<b>Moe</b>
<b>Larry</b>
<b>Curly</b>
When looping over an array of strings, a . can be used to refer to the current
item in the list.
Template:
{{#musketeers}}
* {{.}}
{{/musketeers}}
View:
{
musketeers = { "Athos", "Aramis", "Porthos", "D'Artagnan" }
}
Output:
* Athos
* Aramis
* Porthos
* D'Artagnan
If the value of a section variable is a function, it will be called in the context of the current item in the list on each iteration.
Template:
{{#beatles}}
* {{name}}
{{/beatles}}
View:
{
beatles = {
{ first_name = "John", last_name = "Lennon" },
{ first_name = "Paul", last_name = "McCartney" },
{ first_name = "George", last_name = "Harrison" },
{ first_name = "Ringo", last_name = "Starr" }
},
name = function (self)
return self.first_name .. " " .. self.last_name
end
}
Output:
* John Lennon
* Paul McCartney
* George Harrison
* Ringo Starr
If the value of a section key is a function, it is called with the section's literal block of text, un-rendered, as its first argument. The second argument is a special rendering function that uses the current view as its view argument. It is called in the context of the current view object.
Template:
{{#bold}}Hi {{name}}.{{/bold}}
View:
{
name = "Tater",
bold = function (self)
return function (text, render)
return "<b>" .. render(text) .. "</b>"
end
end
}
Output:
<b>Hi Tater.</b>
An inverted section opens with {{^section}} instead of {{#section}}. The
block of an inverted section is rendered only if the value of that section's tag
is null, undefined, false, or an empty list.
Template:
{{#repos}}<b>{{name}}</b>{{/repos}}
{{^repos}}No repos :({{/repos}}
View:
{
"repos": {}
}
Output:
No repos :(
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 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
variables 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}}
In lustache an object of partials may be passed as the third argument to
lustache:render. The object should be keyed by the name of the partial, and
its value should be the partial text.
Set Delimiter tags start with an equals 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.
lustache uses the lunit testing framework. In order to run the tests you'll need to install lunit, which can be done through luarocks or your choice of lua package manager.
$ luarocks install lunit
Then run the tests.
$ lunit spec/*
lustache began as a direct port of Jan Lehnardt's excellent mustache.js. It would be significantly further behind without the available code from the many contributors. <3
MIT licensed. View LICENSE file for more details.