DevOps Bootcamp · Lesson

tpl: Rendering Strings from Values

Evaluating template expressions stored in values.

Lesson 2 of 413 steps

tpl: Rendering Strings from Values is a free DevOps Bootcamp lesson on CoddyKit. This is lesson 2 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the DevOps Bootcamp learning path, and your progress syncs across the web and the CoddyKit app. The DevOps Bootcamp course includes 4 lessons in total.

Templates Inside Values

Sometimes a value in values.yaml itself contains template syntax. By default Helm treats it as a plain string and never evaluates it.

Meet the tpl Function

The tpl function takes a string and a context, then renders that string as a Go template right where you call it.

{{ tpl .Values.greeting . }}

It Needs a Context

The second argument to tpl is the scope used during rendering. Passing the root dot lets the string reach Values and Release.

{{ tpl "Hello {{ .Release.Name }}" . }}

A Templated Value

Now a user can store a dynamic string in values, like a hostname built from the release name, and have it expand at render time.

host: "{{ .Release.Name }}.example.com"

Rendering That Value

In your template, pass that field through tpl with the root context to turn the stored placeholder into a real value.

host: {{ tpl .Values.host . | quote }}

Why Not Just Reference It

A direct reference prints the raw braces as text. Only tpl actually evaluates the embedded directives inside the stored string.

Rendering Files Too

You can also feed file contents to tpl, letting a bundled config file include release-specific placeholders.

{{ tpl (.Files.Get "config.tpl") . }}

Passing a Custom Scope

The context need not be the root. Pass any dict so the rendered string sees exactly the variables you choose.

{{ tpl .Values.msg (dict "name" "api") }}

A Real Use Case

Charts often let users template ingress hosts or annotations this way, keeping flexible config in values rather than templates.

Mind the Errors

If the stored string has a typo, tpl fails at render time, so test with helm template after adding templated values.

Combine with quote

Since a templated host can contain dots or colons, pipe the tpl result through quote so the final YAML value stays a safe string.

host: {{ tpl .Values.host . | quote }}

Quick Check

Quick check on tpl behavior.

Recap

You learned that tpl evaluates template strings stored in values or files, using a context you supply such as the root dot. 🎉

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Frequently Asked Questions

Is the “tpl: Rendering Strings from Values” lesson free?

Yes — any 3 lessons of the DevOps Bootcamp learning path, including “tpl: Rendering Strings from Values”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The DevOps Bootcamp course includes 4 lessons in total.

What will I learn in “tpl: Rendering Strings from Values”?

Evaluating template expressions stored in values. You practise DevOps Bootcamp with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start DevOps Bootcamp?

No prior experience is required. DevOps Bootcamp on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 4.

How long does the “tpl: Rendering Strings from Values” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this DevOps Bootcamp lesson?

Yes. Every DevOps Bootcamp lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Deep Merge with mergeOverwrite and dict
  2. tpl: Rendering Strings from Values
  3. Looping Files with range Over .Files.Glob
  4. fail and Custom Validation Guards
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