Template language

Templates are HTML with values written in — the language of the editor's Code view, a subset of Twig. A value the data does not give prints empty, and is named in the ReflowPDF-Missing-Variables header (or missing_variables of the JSON response). Output is HTML-escaped unless it passes through |raw.

Values#

<h1>Invoice {{ invoice.number }}</h1>
<p>{{ customer.name|upper }} · {{ invoice.date|date('F j, Y') }}</p>
<p>Total: {{ total|currency('USD') }}</p>
<p>{{ note|default('Thank you for your business.') }}</p>
<p>{{ paid ? 'Paid' : 'Due ' ~ invoice.due }}</p>

Loops and conditions#

<table>
  {% for item in items %}
    <tr class="{{ loop.index % 2 == 1 ? 'odd' : '' }}">
      <td>{{ loop.index }}</td>
      <td>{{ item.description }}</td>
      <td>{{ (item.quantity * item.price)|number_format(2) }}</td>
    </tr>
  {% else %}
    <tr><td colspan="3">No items.</td></tr>
  {% endfor %}
</table>

{% if balance > 0 %}
  <p class="due">Balance due: {{ balance|currency('EUR') }}</p>
{% elif balance == 0 %}
  <p>Paid in full.</p>
{% endif %}

{% set subtotal = 0 %}
{# a comment: not printed #}

{% elif %} may also be written {% elseif %}, as Twig spells it.

Operators#

• Comparison ==, !=, <, >, <=, >=; logic and, or, not (or &&, ||, !).
• Arithmetic +, -, *, /, %, ** (a power: 2 ** 10); text joined with ~.
• in (a value in a list or text), starts with, ends with; ranges 1..5.
• Choice a ? b : c, b if a else c; a ?: b (a when it is true, that is not empty and not zero; else b); a ?? b (a when it is there and not null, else b).
• Tests is and is not: odd, even, empty, defined, null, iterable, divisible by(3), same as(x) — {{ loop.index is odd ? "shade" : "" }}.

A template that does not read (an expression, a tag or a filter the language cannot parse) is not printed half-read: the API answers 400 template_error with each place, the editor marks it.

Arithmetic takes numbers, and what stands for none: an absent value, null, "", true/false. Text that is no number is said where it is (template_error), never printed as 0: "Total: " ~ subtotal + tax adds tax to the text, as Twig reads it.

A fill has a budget: 1,000,000 loop iterations (a range counts its length before it is made: 1..10000000 stops at once) and 20,000,000 characters, of the output and of any one text a value grows to. A document of real size is far below — a table of 10,000 rows of 20 cells is 200,000 iterations; past it, template_error names the place.

Filters#

Printing the language as text#

{% verbatim %}Write {{ name }} to print a value.{% endverbatim %}