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Goodies

GRMustache ships with a library of built-in goodies available for your templates.

Formatter

GRMustache provides built-in support for Foundation's Formatter and its subclasses such as NumberFormatter and DateFormatter.

Formatting a value

let percentFormatter = NumberFormatter()
percentFormatter.numberStyle = .percent

let template = try! Template(string: "{{ percent(x) }}")
template.register(percentFormatter, forKey: "percent")

// Rendering: 50%
let data = ["x": 0.5]
let rendering = try! template.render(data)

Formatting all values in a section

Formatters are able to format all variable tags inside the section:

Document.mustache:

{{# percent }}
hourly: {{ hourly }}
daily: {{ daily }}
weekly: {{ weekly }}
{{/ percent }}

Rendering code:

let percentFormatter = NumberFormatter()
percentFormatter.numberStyle = .percent

let template = try! Template(named: "Document")
template.register(percentFormatter, forKey: "percent")

// Rendering:
//
//   hourly: 10%
//   daily: 150%
//   weekly: 400%

let data = [
    "hourly": 0.1,
    "daily": 1.5,
    "weekly": 4,
]
let rendering = try! template.render(data)

Variable tags buried inside inner sections are escaped as well, so that you can render loop and conditional sections. However, values that can't be formatted are left untouched:

Document.mustache:

{{# percent }}
  {{# ingredients }}
  - {{ name }}: {{ proportion }}  {{! name is intact, proportion is formatted. }}
  {{/ ingredients }}
{{/ percent }}

Would render:

- bread: 50%
- ham: 22%
- butter: 43%

Precisely speaking, "values that can't be formatted" are the ones that have the string(for:) method return nil, as stated by NSFormatter documentation.

Typically, NumberFormatter only formats numbers, and DateFormatter, dates: you can safely mix various data types in a section controlled by those well-behaved formatters.

Support for Formatter is written using public APIs. You can check the source for inspiration.

HTMLEscape

Usage:

let template = ...
template.register(StandardLibrary.HTMLEscape, forKey: "HTMLEscape")

As a filter, HTMLEscape returns its argument, HTML-escaped.

<pre>
   {{ HTMLEscape(content) }}
</pre>

When used in a section, HTMLEscape escapes all inner variable tags in a section:

{{# HTMLEscape }}
  {{ firstName }}
  {{ lastName }}
{{/ HTMLEscape }}

Variable tags buried inside inner sections are escaped as well, so that you can render loop and conditional sections:

{{# HTMLEscape }}
  {{# items }}
    {{ name }}
  {{/}}
{{/ HTMLEscape }}

StandardLibrary.HTMLEscape is written using public APIs. You can check the source for inspiration.

See also javascriptEscape, URLEscape

javascriptEscape

Usage:

let template = ...
template.register(StandardLibrary.javascriptEscape, forKey: "javascriptEscape")

As a filter, javascriptEscape outputs a Javascript and JSON-savvy string:

<script type="text/javascript">
  var name = "{{ javascriptEscape(name) }}";
</script>

When used in a section, javascriptEscape escapes all inner variable tags in a section:

<script type="text/javascript">
  {{# javascriptEscape }}
    var firstName = "{{ firstName }}";
    var lastName = "{{ lastName }}";
  {{/ javascriptEscape }}
</script>

Variable tags buried inside inner sections are escaped as well, so that you can render loop and conditional sections:

<script type="text/javascript">
  {{# javascriptEscape }}
    var firstName = {{# firstName }}"{{ firstName }}"{{^}}null{{/}};
    var lastName = {{# lastName }}"{{ lastName }}"{{^}}null{{/}};
  {{/ javascriptEscape }}
</script>

StandardLibrary.javascriptEscape is written using public APIs. You can check the source for inspiration.

See also HTMLEscape, URLEscape

URLEscape

Usage:

let template = ...
template.register(StandardLibrary.URLEscape, forKey: "URLEscape")

As a filter, URLEscape returns its argument, percent-escaped.

<a href="http://google.com?q={{ URLEscape(query) }}">...</a>

When used in a section, URLEscape escapes all inner variable tags in a section:

{{# URLEscape }}
  <a href="http://google.com?q={{query}}&amp;hl={{language}}">...</a>
{{/ URLEscape }}

Variable tags buried inside inner sections are escaped as well, so that you can render loop and conditional sections:

{{# URLEscape }}
  <a href="http://google.com?q={{query}}{{#language}}&amp;hl={{language}}{{/language}}">...</a>
{{/ URLEscape }}

StandardLibrary.URLEscape is written using public APIs. You can check the source for inspiration.

See also HTMLEscape, javascriptEscape

each

Usage:

let template = ...
template.register(StandardLibrary.each, forKey: "each")

Iteration is natural to Mustache templates: {{# users }}{{ name }}, {{/ users }} renders "Alice, Bob, etc." when the users key is given a list of users.

The each filter is there to give you some extra keys:

  • @index contains the 0-based index of the item (0, 1, 2, etc.)
  • @indexPlusOne contains the 1-based index of the item (1, 2, 3, etc.)
  • @indexIsEven is true if the 0-based index is even.
  • @first is true for the first item only.
  • @last is true for the last item only.
Users with their positions:
{{# each(users) }}
- {{ @indexPlusOne }}: {{ name }}
{{/}}

Comma-separated user names:
{{# each(users) }}{{ name }}{{^ @last }}, {{/}}{{/}}.

Users with their positions:
- 1: Alice
- 2: Bob
- 3: Craig

Comma-separated user names: Alice, Bob, Craig.

When provided with a dictionary, each iterates each key/value pair of the dictionary, stores the key in @key, and sets the value as the current context:

{{# each(items) }}
- key: {{ @key }}, value: {{.}}
{{/}}
- key: name, value: Alice
- key: score, value: 200
- key: level, value: 5

The other positional keys @index, @first, etc. are still available when iterating dictionaries.

The each filter is written using public APIs. You can check the source for inspiration.

zip

Usage:

let template = ...
template.register(StandardLibrary.zip, forKey: "zip")

The zip filter iterates several lists all at once. On each step, one object from each input list enters the rendering context, and makes its own keys available for rendering.

Document.mustache:

{{# zip(users, teams, scores) }}
- {{ name }} ({{ team }}): {{ score }} points
{{/}}

Data:

[
  "users": [
    [ "name": "Alice" ],
    [ "name": "Bob" ],
  ],
  "teams": [
    [ "team": "iOS" ],
    [ "team": "Android" ],
  ],
  "scores": [
    [ "score": 100 ],
    [ "score": 200 ],
  ]
]

Rendering:

- Alice (iOS): 100 points
- Bob (Android): 200 points

In the example above, the first step has consumed (Alice, iOS and 100), and the second one (Bob, Android and 200).

The zip filter renders a section as many times as there are elements in the longest of its argument: exhausted lists simply do not add anything to the rendering context.

The zip filter is written using public APIs. You can check the source for inspiration.

Localizer

Usage:

let template = ...

let localizer = StandardLibrary.Localizer(bundle: nil, table: nil)
template.register(localizer, forKey: "localize")

Localizing a value

As a filter, localize outputs a localized string:

{{ localize(greeting) }}

This would render Bonjour, given Hello as a greeting, and a French localization for Hello.

Localizing template content

When used in a section, localize outputs the localization of a full section:

{{# localize }}Hello{{/ localize }}

This would render Bonjour, given a French localization for Hello.

Localizing template content with embedded variables

When looking for the localized string, GRMustache replaces all variable tags with "%@":

{{# localize }}Hello {{name}}{{/ localize }}

This would render Bonjour Arthur, given a French localization for Hello %@. String(format:) is used for the final interpolation.

Localizing template content with embedded variables and conditions

You can embed conditional sections inside:

{{# localize }}Hello {{#name}}{{name}}{{^}}you{{/}}{{/ localize }}

Depending on the name, this would render Bonjour Arthur or Bonjour toi, given French localizations for both Hello %@ and Hello you.

StandardLibrary.Localizer filter is written using public APIs. You can check the source for inspiration.

Logger

Usage:

let template = ...

let logger = StandardLibrary.Logger { print($0) }
template.extendBaseContext(logger)

Logger is a tool intended for debugging templates.

It logs the rendering of variable and section tags such as {{name}} and {{#name}}...{{/name}}.

To activate logging, add a Logger to the base context of a template:

let template = try! Template(string: "{{name}} died at {{age}}.")

// Logs all tag renderings with NSLog():
let logger = StandardLibrary.Logger()
template.extendBaseContext(logger)

// Render
let data = ["name": "Freddy Mercury", "age": 45]
let rendering = try! template.render(data)

In the log:

{{name}} at line 1 did render "Freddy Mercury" as "Freddy Mercury"
{{age}} at line 1 did render 45 as "45"