Macro

A macro is a piece of code given a name so it can be called from another part of the template. To declare a macro you use the macro instruction. For example:

{% macro title %}A beautiful book{% end %}

defines a macro named title. A macro is a function, so to call it you use parentheses ( and ):

{{ title() }}
A beautiful book

Inside a macro, you can access not only global variables, but also variables and macros declared earlier in the same file. For example:

{% var prodotto = "tablet" %}
{% macro title %}A beautiful {{ prodotto }}{% end %}

{{ title() }}
A beautiful tablet

A variable declared inside a macro is not visible outside the macro itself.

Endless macros

If a macro has no parameters and there are no other instructions after the macro declaration, you can omit {% end %} or {% end macro %} at the end. The macro ends at the end of the file.

Endless macros are written without the macro keyword and with a capitalized first letter:

{% Main %}

In the following example, Main is an endless macro and therefore extends to the end of the file.

{% extends "layout.html" %}
{% Main %}

<ul>
  {% for product in products %}
  <li><a href="{{ product.URL }}">{{ product.Name }}</a></li>
  {% end for %}
</ul>

The previous example is equivalent to writing

{% extends "layout.html" %}
{% macro Main %}

<ul>
  {% for product in products %}
  <li><a href="{{ product.URL }}">{{ product.Name }}</a></li>
  {% end for %}
</ul>

{% end macro %}

Macros with parameters

A macro can have parameters, like any other function. These are declared inside parentheses ( and ), separated by a comma ,, and in addition to the parameter name you must specify the type.

The following instruction declares a macro named image with three parameters.

{% macro image(url string, width int, height int) %}
  <img src="{{ url }}" width="{{ width }}" height="{{ height }}">
{% end %}

A macro must be called with the same number of arguments, in the same order and of the same type as the parameters in its declaration.

{{ image("picture.jpg", 400, 500) }}
<img src="picture.jpg" width="400" height="500">

A type can be omitted if the next parameter has the same type. The previous declaration can therefore be rewritten as:

{% macro image(url string, width, height int) %}
  <img src="{{ url }}" width="{{ width }}" height="{{ height }}">
{% end %}

Calling a macro declared in another file

To call a macro declared in another file, such as a file that declares macros used in various parts of the template, you must first import the file with the import instruction.

{% import "/imports/images.html" %}

{{ Image("offer.png", 200, 200) }}
<img src="offer.png" width="200" height="200">

Macros declared in other files must have a capitalized first letter in their name in order to be imported.