Working with Template Functions

1. Accessing Values ({{ .Values.key }})

Expression	Result
`{{ .Values.replicaCount }}`	Top-level scalar
`{{ .Values.image.repository }}`	Nested field
`{{ index .Values "weird-key" }}`	Key with dashes/dots
`{{ .Values.missing \| default "x" }}`	Safe access with fallback

2. Using Pipeline Operations

Example: Chained transformations

name: {{ .Values.appName | lower | trunc 63 | trimSuffix "-" | quote }}

3. Quoting Strings

Function	Output
`quote`	Wraps in double quotes
`squote`	Wraps in single quotes
`printf "%q" .`	Go-style quoted string

4. Converting to YAML

Example: Render arbitrary structure

nodeSelector:
  {{- toYaml .Values.nodeSelector | nindent 2 }}
tolerations:
  {{- toYaml .Values.tolerations | nindent 2 }}

5. Converting to JSON

Function	Use
`toJson`	Compact JSON
`toPrettyJson`	Indented JSON
`fromJson`	Parse JSON string into map

6. Using Default Values

Example: Fallback chain

tag: {{ .Values.image.tag | default .Chart.AppVersion | quote }}
host: {{ .Values.host | default "localhost" }}
port: {{ .Values.port | default 8080 }}

7. String Manipulation

Function	Effect
`upper / lower / title`	Case conversion
`trim / trimAll / trimPrefix / trimSuffix`	Strip whitespace/chars
`trunc N`	Limit to N characters
`replace "a" "b" .`	String replace
`contains "sub" .`	Boolean substring check
`split "/" .`	Returns dict `_0`, `_1`...
`splitList "/" .`	Returns true list
`printf "%s-%d" .Name 1`	Formatted string

8. Type Conversion

Function	Converts to
`toString`	String
`int / int64 / atoi`	Integer
`float64`	Float
`toJson / fromJson`	JSON
`toYaml / fromYaml`	YAML
`typeOf .`	Reflect type name
`kindOf .`	Underlying kind (string, map, slice...)

9. Encoding Functions

Function	Use
`b64enc / b64dec`	Base64
`b32enc / b32dec`	Base32
`sha1sum / sha256sum`	Hashing (for checksum annotations)
`adler32sum`	Adler-32 checksum

10. Date Functions

Function	Result
`now`	Current `time.Time`
`date "2006-01-02" now`	Format using Go reference time
`dateInZone "2006-01-02T15:04:05Z" now "UTC"`	Zone-aware format
`htmlDate / htmlDateInZone`	HTML5 date format

Warning: now changes on every render — it forces rolling updates if used in annotations. Use .Release.Time if you want stability across re-renders.

11. UUID Generation

Example: Random UUID v4

annotations:
  rollout-id: {{ uuidv4 | quote }}

Warning: uuidv4 changes per render — triggers unnecessary pod restarts. Prefer hashing values for stability.

12. Using fail Function

Example: Hard validation

{{- if not .Values.image.repository }}
{{- fail "image.repository is required" }}
{{- end }}
{{- if and .Values.persistence.enabled (not .Values.persistence.size) }}
{{- fail "persistence.size required when persistence.enabled=true" }}
{{- end }}

Function	Behavior
`fail "msg"`	Aborts render with error message
`required "msg" .Values.x`	Aborts if value is nil/empty