Know Your Template Functions

Helm uses Go templates for templatingyour resource files. While Go ships several built-in functions, we haveadded many others.

First, we added almost all of the functions in theSprig library. We removed twofor security reasons: env and expandenv (which would have given chart authorsaccess to Tiller’s environment).

We also added two special template functions: include and required. The includefunction allows you to bring in another template, and then pass the results to othertemplate functions.

For example, this template snippet includes a template called mytpl, thenlowercases the result, then wraps that in double quotes.

value: {{ include "mytpl" . | lower | quote }}

The required function allows you to declare a particularvalues entry as required for template rendering. If the value is empty, the templaterendering will fail with a user submitted error message.

The following example of the required function declares an entry for .Values.whois required, and will print an error message when that entry is missing:

value: {{ required "A valid .Values.who entry required!" .Values.who }}

When using the include function, you can pass it a custom object tree built from the current context by using the dict function:

{{- include "mytpl" (dict "key1" .Values.originalKey1 "key2" .Values.originalKey2) }}