Intro to Jinja

Overview

Rewst uses the Jinja2, aka "Jinja" templating language in text fields to enable more powerful processing of the data that exists in a workflow. Jinja is based on Python and shares much of its syntax and styling, but the key difference is that expressions are encapsulated to separate themselves from plain text in these fields.

The Jinja language is meant to be extensible, and within Rewst there are many filters that extend functionality, including an ever-growing list that Rewst adds to the platform. This means that if you search the web for help with Jinja, the answers you find may or may not be 100% applicable to the Rewst environment. When in doubt, you can always ask the ROC for assistance!

Types of Jinja

Variable Expressions

Variable expressions are encapsulated by double curly braces ({{ and }}) and will output the value of the variable or expression as they are evaluated.

{{ CTX.my_var }}

Control Flow Statements

These are used for decision-making functions such as sets, if statements and for eaches. They are encapsulated by curly+percent signs ({% %})

{% set x = 100 %}

These statements typically do not output anything.

Comments

Comments do nothing. In the Rewst Monaco editor, you can use the hotkey CTRL-/ to comment blocks of code.

{# COMMENT #}

Whitespace

By default, when Jinja begins a statement block, it preserves any whitespace characters (spaces, carriage returns, etc) before or after the block. In many cases, you will want to remove any spaces you did not explicitly intend to have, so the addition of the - character in the open and closing braces will remove the whitespace before or after the statement, respectively.

{%- for part in parts_list -%}
  {{- part.name -}}
{%- endfor -%}

Jinja Resources

Below are some resources, external to Rewst, that can be used to assist during the use of Jinja.

Jinja Docs

Jinja Examples

Note that whilst right now Jinja is required, the plan is to create actions to make this easier for everyday users to manipulate their data and not have to worry about using Jinja at all.

Want more practice?

Check out our Rewst 103: Jinja Essentials for Workflow Automation course.