Tags

A tag is a high level operation, usually representing similar constructions that regular programming languages provide. They perform conditional execution, loops, printing, commenting, etc. Let's check out each of them one-by-one.

Print

Print tag is the most basic statement of all, all it does is it forumlates its body as a string expression.

templateEngine.evaluate("{{ 'This is a string' }}") // This is a string

Print statement is smart, it evaluates its body while using functions, variables, and data type instances.

templateEngine.evaluate("{{ 2 * round(value) }}", variables: ["value": 2.8]) // 6

If and If-Else

It's easy to run conditional evaluation:

Tuxedo().evaluate("{% if true %}Hello{% endif %} {{ name }}!", variables: ["name": "John"]) // Hello John!

You can also use one with an else clause:

Tuxedo().evaluate("{% if greeting %}Hello{% else %}Bye{% endif %} {{ name }}!", variables: ["greeting": false, "name": "John"]) // Bye John!

For

For loop iterates over an array and creates a local variable with every value in the collection:

Tuxedo().evaluate("{% for i in [1,2,3] %}{{i * 2}}{% if i is not last %}, {% endif %}{% endfor %}") // 2, 4, 6

Comment

Comment statement removes its body and replaces it with an empty string, therefore makes its content disappear, as a commented block in regaular programming languages.

templateEngine.evaluate("Hello {# commented block #}World!") // Hello World!

Set

Set creates named variables and assignes values to them.

It can be expressed in two distinct ways:

template.evaluate("{% set x = 4.0 %}")
template.evaluate("{% set x %}this{% endset %}")

Macro

There's also an option to create custom macros (define basic functions):

template.evaluate("{% macro duplicate(value) %}value * 2{% endmacro %}{{ duplicate(4) }}") // 8

Block

You can define blocks which print the body of them.

Tuxedo().evaluate("Title: {% block title %}Original{% endblock %}") // Title: Original

Blocks allows them to override their contents later

{% block title %}Other{% endblock %} // Title: Other

If you need the previous value, you can access it throug the parent method:

{% block title %}{{ parent() }} + New{% endblock %} // Title: Original + New

Or override the parent if it contains any variables:

Tuxedo().evaluate("""

{% block title %}Hello {{name}}{% endblock %}
{% block title %}{{ parent(name='John') }}!{% endblock %}

""", variables: ["name": "Geroge"]) // Hello John

Import

If using template files, it's easy to import one using the import statement:

{% import 'template.txt' %}

It uses a file url path pattern, so subfolder/template.txt works when accessing files in a different folder.

Spaceless

You can wrap your code around spaceless tags to remove every whitespace in the body.

Tuxedo().evaluate("{% spaceless %}   {% if true %}    Hello    {% endif %}    {% endspaceless %}") // Hello

Or, if you only need to eliminate whitespaces on one side, you can use the special {-} notation. If placed anywhere, it removes itself and the whitespaces around it.

Tuxedo().evaluate("asd   {% if true %}   Hello {-}  {% endif %}   ")
← Object functions