Create a custom filter¶

See also

Create custom template filters to change the way variables are rendered in your templates. By following some simple rules, Zotonic will automatically find the filter for you:

Create a file in the src/filters/ directory of your site or module.
Prepend the filter filename with filter_.
Export a function with the name of your filter that corresponds to the filename.

So, let’s say you need to sort a list of items and remove duplicate values from it:

mod_yourmodule/src/filters/filter_uniquesort.erl¶

-module(filter_uniquesort).
-export([uniquesort/2]).
-include_lib("zotonic_core/include/zotonic.hrl").

uniquesort(List, _Context) ->
    lists:usort(List).

The custom uniquesort filter is then available in your templates:

{% for thing in list_of_things|uniquesort %}
    {{ thing }} is now sorted and unique!
{% endfor %}